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1

Cenozoic rifting in the West Antarctic Rift System  

NASA Astrophysics Data System (ADS)

The West Antarctic Rift System (WARS) experienced two episodes of Cenozoic rifting. Seafloor spreading at the Adare spreading axis, north of the Ross Sea, from Middle Eocene to Late Oligocene time (43 - 26 Ma), was directly linked with motions within the WARS. For this time interval, marine magnetic anomalies within the Adare Basin and structural features within the Ross Sea constrain the motion between East and West Antarctica. During this episode, widespread intrusive activity took place in the continental part of the rift. Subsequent Late Oligocene until present-day (26 - 0 Ma) extension was characterized by a transition to volcanic activity. Yet, the details of extension during this episode have been poorly resolved. We present preliminary results of new seismic reflection and seafloor mapping data acquired on geophysical cruise 07-01 aboard the R/VIB Nathaniel Palmer in the northern part of the rift. Our results suggest that the style of deformation changed from spreading-related faulting into diffuse normal faulting (tilted blocks) that trend NE-SW with little resultant E-W extension. Recent volcanism is distributed throughout but tends to align with the NE-SW trend, into a localized zone. Formation of the Terror Rift, Ross Sea, within the same time frame suggests that the pole of rotation has changed its position, reflecting a change in the relative magnitudes of tensile stresses along the rift. Moreover, this change was accompanied with a sharp decrease of extension rates.

Granot, R.; Cande, S. S.; Stock, J. M.; Clayton, R. W.; Davey, F. J.

2004-12-01

2

Cenozoic rifting in the West Antarctic Rift System  

NASA Astrophysics Data System (ADS)

The West Antarctic Rift System (WARS) experienced two episodes of Cenozoic rifting. Seafloor spreading at the Adare spreading axis, north of the Ross Sea, from Middle Eocene to Late Oligocene time (43 - 26 Ma), was directly linked with motions within the WARS. For this time interval, marine magnetic anomalies within the Adare Basin and structural features within the Ross Sea constrain the motion between East and West Antarctica. During this episode, widespread intrusive activity took place in the continental part of the rift. Subsequent Late Oligocene until present-day (26 - 0 Ma) extension was characterized by a transition to volcanic activity. Yet, the details of extension during this episode have been poorly resolved. We present preliminary results of new seismic reflection and seafloor mapping data acquired on geophysical cruise 07-01 aboard the R/VIB Nathaniel Palmer in the northern part of the rift. Our results suggest that the style of deformation changed from spreading-related faulting into diffuse normal faulting (tilted blocks) that trend NE-SW with little resultant E-W extension. Recent volcanism is distributed throughout but tends to align with the NE-SW trend, into a localized zone. Formation of the Terror Rift, Ross Sea, within the same time frame suggests that the pole of rotation has changed its position, reflecting a change in the relative magnitudes of tensile stresses along the rift. Moreover, this change was accompanied with a sharp decrease of extension rates.

Granot, R.; Cande, S. S.; Stock, J. M.; Clayton, R. W.; Davey, F. J.

2007-12-01

3

The Northeast Brazilian Rift System  

Microsoft Academic Search

The northeast Brazilian rift basins provide important data critical to the understanding of continental rifting processes associated with the opening of the South Atlantic. These basins represent the locus of intersection of the Southern and Equatorial branches and some basins yield substantial chronostratigraphic data that constrain the temporal and spatial interaction of the rift phases. Similar data are not found

Renato M. Darros de Matos

1992-01-01

4

Proterozoic Midcontinent Rift System, an overview  

Microsoft Academic Search

The Middle and Late Proterozoic Midcontinent Rift System (MRS) extends across the middle US, from Lake Superior through Wisconsin, Minnesota, Iowa and Nebraska into Kansas on the southwest limb and across upper and lower Michigan on the southeast limb. Exploration for oil and gas generated over 7,000 miles of seismic, a leasehold of near seven million acres, but only three

S. D. Kerr; S. M. Landon

1992-01-01

5

The influence of preexisting structure on the evolution of the Cenozoic Malawi rift (East African rift system)  

Microsoft Academic Search

This paper analyzes the importance of preexisting structure for the evolution of the Cenozoic Malawi rift, which constitutes the southernmost part of the western branch of the East African rift system. Kinematic analyses demonstrate that the regional extension direction rotated clockwise from ENE to SE during rifting. Cenozoic rift faults (of dip-, oblique-, and strike-slip character) rejuvenated crustal structures whenever

Uwe Ring

1994-01-01

6

Proterozoic Midcontinent Rift System, an overview  

SciTech Connect

The Middle and Late Proterozoic Midcontinent Rift System (MRS) extends across the middle US, from Lake Superior through Wisconsin, Minnesota, Iowa and Nebraska into Kansas on the southwest limb and across upper and lower Michigan on the southeast limb. Exploration for oil and gas generated over 7,000 miles of seismic, a leasehold of near seven million acres, but only three test wells. The initial extension of the MRS was marked by filling with layered basalt. Thickness documented by GLIMPCE suggests crustal separation was nearly achieved. The thick dense basalts and thinned pre-rift crust provide high amplitude gravity anomalies which characterize the rift trend. Extension slowed and eventually ceased, creating a sag phase during which clastic sediments were deposited, including sapropelic shale and siltstone, fluvial sandstones and siltstones, and fluvial/alluvial conglomerates. Tectonic inversion to compressional and transpressional forces occurred late in rift history, possibly during part of the period of clastic fill. The MRS trend is highly segmented, with varied tectonic styles, suggesting complex stress systems in its development. The Nonesuch Formation is marine or lacustrine siltstone and shale containing sufficient organic matter to be an effective source rock for oil and gas. Similar facies have been identified along the extent of the western limb, in the subsurface in Minnesota, Iowa and Kansas. TOC values are as high as 3% and maturity ranges from peak oil to advanced. Surface seeps, fluid inclusions, mud log shows and modeling indicate the potential for multiple episodes of generation. Potential reservoir rocks have been identified and seals are present as lacustrine and fluvial shales and possible evaporites. The MRS remains a relatively unexplored frontier hydrocarbon province with giant field potential in the heart of North America.

Kerr, S.D.; Landon, S.M.

1992-01-01

7

The onshore northeast Brazilian rift basins: An early Neocomian aborted rift system  

Microsoft Academic Search

Early Cretaceous rift basins of northeastern Brazil illustrate key three-dimensional geometries of intracontinental rift systems, controlled mainly by the basement structures. These basins were formed and then abandoned during the early extension associated with the north-south-propagating separation of South America and Africa. During the early Neocomian, extensional deformation jumped from the easternmost basins (group 1: Sergipe Alagoas and Gabon basins;

Matos

1990-01-01

8

The Mesoproterozoic Midcontinent Rift System, Lake Superior Region, USA  

NASA Astrophysics Data System (ADS)

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 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.

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

2001-06-01

9

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

Microsoft Academic Search

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

Sarah E. Rilling

2009-01-01

10

Interaction Between Mantle Plume Processes and Surface Topography in Incipient Rift Systems, EARS  

Microsoft Academic Search

In an asymetric extensional setting such as the East African Rift System (EARS), the pronounced regional variations in topography are generally explained by two different models: a) a post-rift uplift resulting from mechanical relaxation that evokes an uplift of the rift shoulders, and b) a syn-rift uplift effected by mantle plume pushing during extension. However, an important pre-rift topographic feature

H. Wichura; R. Bousquet; R. Oberhänsli

2009-01-01

11

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)

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.

Schmeling, Harro; Wallner, Herbert

2012-08-01

12

Petroleum system of the Shelf Rift Basin, East China Sea  

SciTech Connect

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.

Cunningham, A.C.; Armentrout, J.M.; Prebish, M. (Mobil Oil Corp., Dallas, TX (United States)) (and others)

1996-01-01

13

Geochemical Overview of the East African Rift System  

Microsoft Academic Search

Mafic volcanics of the East African Rift System (EARS) record a protracted history of continental extension that is linked to mantle plume activity. The modern EARS traverses two post-Miocene topographic domes separated by a region of polyphase extension in northern Kenya and southern Ethiopia. Basaltic magmatism commenced ˜45 Ma in this highly extended region, while the onset of plume-related activity

T. Furman

2003-01-01

14

Innovative tephra studies in the East African Rift System  

NASA Astrophysics Data System (ADS)

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.

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

15

Seismic-refraction studies of the Afro-Arabian rift system — a brief review  

Microsoft Academic Search

The crustal and uppermost-mantle structure of major units of the Afro-Arabian rift system has been consecutively investigated by seismic-refraction surveys in the Jordan-Dead Sea rift, the Red Sea, the Afar depression and the East African rift of Kenya. With the exception of the Jordan-Dead Sea transform, the entire Afro-Arabian rift system is underlain by anomalous mantle with Pn-velocities less than

C. Prodehl; K. Fuchs; J. Mechie

1997-01-01

16

The onshore northeast Brazilian rift basins: An early Neocomian aborted rift system  

SciTech Connect

Early Cretaceous rift basins of northeastern Brazil illustrate key three-dimensional geometries of intracontinental rift systems, controlled mainly by the basement structures. These basins were formed and then abandoned during the early extension associated with the north-south-propagating separation of South America and Africa. During the early Neocomian, extensional deformation jumped from the easternmost basins (group 1: Sergipe Alagoas and Gabon basins; group 2: Reconcavo, Tucano, and Jatoba basins) to the west, forming a series of northeast-trending intracratonic basins (group 3: Araripe, Rio do Peixe, Iguatu, Malhada Vermelha, Lima Campos, and Potiguar basins). The intracratonic basins of groups 2 and 3 consist of asymmetric half-grabens separated by basement highs, transfer faults, and/or accommodation zones. These basins are typically a few tens of kilometers wide and trend northeast-southwest, roughly perpendicular to the main extension direction during the early Neocomian. Preexisting upper crustal weakness zones, like the dominantly northeast-southwest-trending shear zones of the Brazilian orogeny, controlled the development of intracrustal listric normal faults. Internal transverse structures such as transfer faults (Reconcavo basin and onshore Potiguar basin) and accommodation zones (onshore Potiguar basin and Araripe basin) were also controlled by the local basement structural framework. Transverse megafaults and lithostructural associations controlled the three main rift trends. The megashear zones of Pernanbuco (Brazil)-Ngaundere (Africa) apparently behaved like a huge accommodation zone, balancing extensional deformation along the Reconcavo-Jatoba/Sergipe Alagoas-Gabon trends with simultaneous extension along the Araripe-Potiguar trend. The Sergipe Alagoas-Gabon trend and the Potiguar basin represent the site of continued evolution into a marginal open basin following early Neocomian deformation.

Matos, R. (Cornell Univ., Ithaca, NY (USA))

1990-05-01

17

Volcanism, tectonism, sedimentation, and the paleoanthropological record in the Ethiopian Rift System  

Microsoft Academic Search

The Ethiopian Rift System consists of basins that are in different stages of evolu- tion. Some of the rift-related basins in southwestern Ethiopia are half-grabens that have not evolved to symmetrical rifts since the initiation of rifting here in the middle Miocene. These basins contain fossiliferous Pliocene-Pleistocene volcaniclastic sedi- ments and volcanic rocks and have been occupied by early hominid

Giday WoldeGabriel; Grant Heiken; Tim D. White; Berhane Asfaw; William K. Hart; Paul R. Renne

2000-01-01

18

Seismicity of the Woodlark-D'Entrecasteaux Rift System in Eastern Papua New Guinea  

Microsoft Academic Search

The Woodlark-D'Entrecasteaux rift system may be the fastest opening continental rift on the planet, accommodating 25-40 mm\\/yr extension in continental crust. Along strike, extension rates increase and rifting has progressed to full sea floor spreading. We report on the results from the first local earthquake survey in the region, across the transition from oceanic rifting to distributed continental extension. From

A. Ferris; B. C. Zelt; G. A. Abers; J. S. Floyd; B. Taylor; J. C. Mutter; A. Lerner-Lam

2002-01-01

19

The West Antarctic Rift System - some outstanding issues  

NASA Astrophysics Data System (ADS)

The West Antarctic Rift System (WARS) is the product of several phases of deformation since the Jurassic with an early history related to that of New Zealand and Tasmania. Several outstanding issues exist in reconstructing the evolution of the West Antarctic Rift System. An early (mid-Cretaceous) intracontinental extensional episode led to the broad crustal thinning of WARS. Recent models propose a 50 km thick crust prior to the onset of extension, but the broad evidence for this is equivocal, as it must have also affected Tasmania and southern New Zealand as well as Antarctica prior to break-up of this part of Gondwana. Several more recent extensional episodes, largely W-E extension, have been proposed, in the early, mid and late Cenozoic, that give rise to a series of N-S trending extensional sedimentary basins. How well are these episodes defined, spatially distributed and how do they relate to a further hypothesis that NW-SE dextral strike slip faulting has had a dominant influence on this extension and basin formation? WARS sedimentary basins are moderately well defined under the Ross Sea, although their age of origin is often not well constrained, but their extension under the Ross Ice Shelf is also controversial. Gravity data have been used to infer their existence but the limited seismic data available do not confirm these models. A direct relationship between the Transantarctic Mountains (TAM), a major mountain range forming the major rift margin of the WARS, and the extensional structures is also equivocal as a major sedimentary basin in the adjacent rift floor only occurs along part of the rift margin.

Davey, F. J.

2010-12-01

20

Geochemical Overview of the East African Rift System  

NASA Astrophysics Data System (ADS)

Mafic volcanics of the East African Rift System (EARS) record a protracted history of continental extension that is linked to mantle plume activity. The modern EARS traverses two post-Miocene topographic domes separated by a region of polyphase extension in northern Kenya and southern Ethiopia. Basaltic magmatism commenced ˜45 Ma in this highly extended region, while the onset of plume-related activity took place ˜30 Ma with eruption of flood basalts in central Ethiopia. A spatial and temporal synthesis of EARS volcanic geochemistry shows progressive lithospheric removal (by erosion and melting) as the degree of rifting increases, with basalts in the most highly extended areas recording melting of depleted asthenosphere. Plume contributions are indicated locally in the northern half of the EARS, but are absent from the southern half. The geochemical signatures are compatible with a physical model in which the entire EARS is fed by a discontinuous plume emanating from the core-mantle boundary as the South African Superswell. Quaternary basaltic lavas erupted in the Afar triangle, Red Sea and Gulf of Aden define the geochemical signature attributed to the Afar plume (87Sr/86Sr 0.7034-0.7037, 143Nd/144Nd 0.5129-0.5130; La/Nb 0.6-0.9; Nb/U 40-50). These suites commonly record mixing with ambient upper mantle having less radiogenic isotopes but generally overlapping incompatible trace element abundances. Within the Ethiopian dome both lithospheric and sub-lithoshperic contributions can be documented clearly; lithospheric contributions are manifest in more radiogenic isotope values (87Sr/86Sr up to 0.7050) and distinctive trace element abundances (e.g., La/Nb <2.0, Nb/U > 10). The degree of lithospheric contribution is lowest within the active Main Ethiopian Rift and increases towards the southern margin of the dome. The estimated depth of melting (65-75 km) is consistent with geophysical observations of lithospheric thickness. In regions of prolonged volcanism the lithospheric contributions and estimated melting depths decrease through time, corresponding to a higher degree of rifting. In the Kenyan dome, including the western rift, the degree of extension is low and lithospheric melting is the dominant source for basaltic magmatism. Mafic lavas from these regions have generally lower MgO but higher contents of alkalis, P2O5 and many incompatible trace elements than are observed in the Ethiopian Rift. High values of 87Sr/86Sr, 207Pb/204Pb and Zr/Hf relative to other parts of the EARS indicate melting of metasomatized lithosphere. Melting in this area occurs at depths up to 100+ km, consistent with the thick crustal section observed seismically. Between the topographic domes, basalts from the Turkana region record melting at shallow levels ( ˜35 km) consistent with seismic evidence for nearly complete rifting of the crustal section. The geochemistry of these lavas is dominated by asthenospheric source materials, with only minor lithospheric involvement. Temporal evolution of EARS geochemistry reflects progressive rifting of the thick craton. This change is manifest within lavas that are interpreted as plume-derived, as Tb/Yb values decrease from 30 Ma through the present. The modern thermal anomaly associated with Afar volcanism does not appear to extend below the shallow mantle, but may reflect a large blob of deep mantle material that became stuck to Africa 30 Ma and has contributed to regional volcanism ever since. Relative contributions from this deep mantle source, shallow asthenosphere and lithosphere are controlled by the extent of rifting and cannot be predicted solely on the basis of surface topography.

Furman, T.

2003-12-01

21

Benue trough and the mid-African rift system  

SciTech Connect

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.

Thomas, D. [Thomas and Associates, Hastings (United Kingdom)

1996-01-29

22

Structure of the basins of the White Sea rift systems  

NASA Astrophysics Data System (ADS)

For the first time, the structure of the sedimentary basins of the Late Proterozoic rift system in the White Sea is characterized based on a set of new marine geological geophysical data such as the results of the common depth point seismic method, gravity and magnetic data, and seismoacoustics. The main tectonic structures in the topography of the heterogeneous basement within the basin of the White Sea are distinguished and described. A structural tectonic scheme of the basement surface is presented. The thicknesses of the sediments are estimated and the stratigraphic confinement of the seismic units recognized is done.

Zhuravlev, V. A.; Shipilov, E. V.

2008-02-01

23

Tectonic inheritance and continental rift architecture: Numerical and analogue models of the East African Rift system  

Microsoft Academic Search

The western branch of the East African Rift is composed of an arcuate succession of elongate asymmetric basins, which differ in terms of interaction geometry, fault architecture and kinematics, and patterns of uplift\\/subsidence and erosion\\/sedimentation. The basins are located within Proterozoic mobile belts at the edge of the strong Tanzanian craton; surface geology suggests that the geometry of these weak

Giacomo Corti; Jolante van Wijk; Sierd Cloetingh; Chris K. Morley

2007-01-01

24

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

NASA Astrophysics Data System (ADS)

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.

Rilling, Sarah E.

25

Interaction Between Mantle Plume Processes and Surface Topography in Incipient Rift Systems, EARS  

NASA Astrophysics Data System (ADS)

In an asymetric extensional setting such as the East African Rift System (EARS), the pronounced regional variations in topography are generally explained by two different models: a) a post-rift uplift resulting from mechanical relaxation that evokes an uplift of the rift shoulders, and b) a syn-rift uplift effected by mantle plume pushing during extension. However, an important pre-rift topographic feature can be documented in the Kenya rift. The pre-rift Yatta Plateau (13.5 Ma) is a phonolitic lava flow with a length of appr. 290 km that flowed eastward, away from the present-day eastern rift shoulder of the Kenya rift. Due to the combination of flow within a pre-existent river valley and later erosional processes the flow is now characterized by relief inversion. At present this river runs exactly parallel to its paleo-valley and erodes its western flank. We reconstruct the paleo-topography by estimating the pre-rift slope and assuming an active lava flow. Viscosities, derived from phonolitic and basaltic bulk rock compositions cooling down from their eruption temperature, permits the calculation of the lava flow velocity. The appliance of this method to unravel the history of this volcanic feature allows us to draw conclusions on the geometry of the central EARS and proves the existence of high topography and relief contrasts along its recent rift axis since appr. 14 Ma, prior to the extension. We propose that the topography is due to a pre-rift uplift caused by thermal expansion of the lithospheric rocks and effected by a heating mantle plume.

Wichura, H.; Bousquet, R.; Oberhänsli, R.

2009-04-01

26

Fluid history in hyper-extended rifted margins: Examples from the fossil Alpine and western Pyrenean rift systems and the present-day Iberia rifted continental margin.  

NASA Astrophysics Data System (ADS)

The evolution of deep-water, magma-poor rifted margins is intimately linked with complex and polyphase fault structures. These structures, known as detachment faults, are responsible for extreme crustal thinning and mantle exhumation. During the evolution of detachment faults fluid-rock interaction plays an important role, changing the chemical and physical properties of rocks. These processes likely have major implications for the strain localization and structural evolution of the margin. The change in rock chemistry and rheology is best indicated by the breakdown of feldspars and olivine into clay and serpentine minerals and the pervasive cementation and precipitation of quartz along the fault zones. Although the chemical and mineral reactions are well known, it is still unclear to what extent these reactions lead to changes in the overall rheology of the extending lithosphere and how they can affect the thermal evolution of the hyper-extended rifted margins. In order to answer to these questions it is important to understand the origin, timing, pathways and composition of the fluids generated during rifting. Are fluids solely of marine origin or do they have a metamorphic- or mantle-derived component? Can we determine the range of temperature and consequently at what depth these fluids are formed? And can we constrain the age of their migration? These questions can be addressed in the well-known hyper-extended rift systems such as the Alpine Tethys margins exposed in the Alps, the Mauléon basin in the Western Pyrenees and the Deep Iberia margin drilled and seismically imaged offshore Portugal. All of these rift settings show evidence for detachment systems associated with hyper-extension and mantle exhumation. The aim of this ongoing study is to characterize the fluid signature in hyper-extended domain in magma-poor rifted margins. Including different sites with different degrees of compressional and metamorphic overprint enables us to compare results and to define the general importance of fluid systems in the development of hyper-extended rifts systems. The first results show that in all three geological settings fluid percolation can be recognized in fault rocks linked to the detachment systems. Evidence for the presence of fluids comes from the analyses of hydration reactions in fault zones. In the Alps the major and trace elements show a gain in elements typical from mantle rocks (Mg, Ni, Cu, Co, V). In the Pyrenees, microstructural studies show that detachment faulting crossed a range of crustal depths providing constraints on the depths of fluid migration. Future analyses will focus on additional major and trace elements and isotopic ratios (Sr and B) of hydrated rocks recovered from these hyper-extended domains, which will be linked with the temporal and spatial evolution of the major detachment structures.

Pinto, Victor Hugo; Manatschal, Gianreto; Karpoff, Anne Marie; Masini, Emmanuel; Lemarchand, Damien; Hayman, Nicholas; Trow, Rudolph; Viana, Adriano

2013-04-01

27

The stratigraphic architecture of hyper-extended rift systems: A field perspective from Aps, Pyrenees and Baja-California  

NASA Astrophysics Data System (ADS)

The discovery of hyper-extended domains in deep water rifted margins challenged the classical view of the evolution of rift systems leading to continental breakup. In these hyper-extended domains, rift basins occur over less than 10km thick extended continental crust or exhumed subcontinental mantle. Neither their imaged stratigraphic architecture and drilled facies nor the subsidence history can be explained by classical McKenzie-type rift models. Studies performed on off- and on-shore examples demonstrate the importance of tectonic exhumation by detachment faulting. However, despite their apparent widespread occurrence in present-day rifted margins, the overall tectono-sedimentary evolution of these systems remains poorly understood. In this study we review and compare key multi-scale observations from 3 different hyper-extended rift systems. 1) The first example, in the Western Pyrenees, corresponds to a complete sediment-rich Cretaceous hyper-extended rift system that can be investigated. 2) The second example in the Swiss Alps, gives the access to supra-detachment sedimentary evolution in a sediment-starved context. 3) The last example exposed in Baja California Sur, shows supra-detachment sedimentary evolution in sediment-rich and shallow water environment. Based on these studies in three different settings, we conclude that the basins forming in the lower and upper plate position respective to detachment fault polarity develop as two different types of basins. Lower plate basins develop over top-basement detachment systems and discontinuous pieces of pre-rift strata (extensional allochthons). In this setting, the sequential development of low-angle detachment systems implies the creation of new real estate crust (new seafloor surfaces) and a complex syn-rift stratigraphic architecture. Through this domain, the deposition of syn- and post-tectonic sediments above exhumation surfaces are diachronous along stretching direction illustrating relative migration of exhumation processes. Syn-tectonic deposits correspond to the erosion of exhumed material and mass-wasting processes along active detachment fault scarps. Once active exhumation migrates, inactive parts of detachment merge to form a lower plate sag basin under thermal subsidence. In contrast, the upper plate basin records a single isochronous sag phase over weakly extended pre-rift strata. This observation suggests that upper plate sag formation is controlled by depth-dependent crustal extension. As illustrated by the different study cases, the sag phase sedimentary record of upper and lower plate settings strongly depends on their respective connection with sediment sourcing systems. Finally, we used the Rifter software developed within the Margin Modelling Phase 3 (MM3) consortium to generate equilibrated lithospheric sections based on our observations. Through these kinematic numerical experiments, we aim to quantify the tectonic, thermal and isostatic evolution of hyper-extended rift systems.

Masini, Emmanuel; Manatschal, Gianreto; Tugend, Julie; Mohn, Geoffroy; Robin, Cécile; Geoffroy, Laurent; Unternehr, Patrick

2013-04-01

28

Earthquakes along the East African Rift System: A multiscale, system-wide perspective  

NASA Astrophysics Data System (ADS)

On the basis of a comprehensive data set of precisely determined depths of 121 large to moderate-sized earthquakes along and near the entire East African Rift System (EARS), there are three distinct patterns in focal depths which seem to correlate with progressive stages in the development of the largest active rift in the world. First, away from both ends of the western, younger branch of the EARS, very large (Mw ? 7) earthquakes occurred in the top 15 km of the crust where surficial expressions of rifting are yet to appear. Curiously, there are unusually deep aftershocks reaching down to 35 ± 3 km. Second, under well-developed but amagmatic rift segments, focal depths show a bimodal distribution, with peaks centered near depths of about 15 ± 5 km and 35 ± 5 km. This pattern is present both under the main axis of the EARS, where rift zone have lengths approaching 1000 km, and beneath rift units 10 times shorter in length. Underside reflections off the Moho indicate that at least part of the second peak in seismicity is due to mantle earthquakes down to 44 ± 4 km, attesting to high differential stress in the mantle lithosphere which is capable of accumulating seismogenic, elastic strain (the "jelly sandwich" rheology). Third, beneath magmatic segments of well-developed rifts, seismicity is largely confined to the upper 15 km of the crust as observed previously, akin to the pattern along mid-ocean ridges where plastic flow due to high temperature inhibits accumulation of shear stress deep in the lithosphere.

Yang, Zhaohui; Chen, Wang-Ping

2010-12-01

29

West Antarctic Rift System: Extension and Collapse of a West Antarctic Plateau  

NASA Astrophysics Data System (ADS)

Recent thermochronologic data along the Byrd Glacier Outlet of the Transantarctic Mountains are consistent with the hypothesis that the West Antarctic Rift System developed during the extension and collapse of a West Antarctic Plateau. Apatite fission track ages of samples collected along the length of the outlet vary from Early Cretaceous (~112 Ma) to Oligocene (~32 Ma). The ages vary in a systematic fashion: older ages are found at higher elevations and/or towards the East Antarctic Craton, while younger samples are located at lower elevations and/or towards the Ross Sea end of the outlet. This systematic variation in ages is consistent with a Cretaceous stage of incision by rivers flowing from West Antarctica towards the craton, followed by Tertiary incision by rivers flowing in the reverse direction, with a final, Oligocene, stage of incision by glacial erosion. This cooling evolution and proposed switch in drainage direction is consistent with other evidence suggesting the presence and collapse of a West Antarctic Plateau including: 1) geodynamic models of extension and thinning of the West Antarctic Rift System, and 2) geomorphic evidence of major paleo-drainage systems flowing through the TAM from West Antarctic into East Antarctica. Although no one piece of evidence is conclusive in and of itself, taken in toto, the evidence is best explained by the presence and subsequent collapse of a West Antarctic Plateau.

Huerta, A. D.; Blythe, A. E.

2010-12-01

30

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

NASA Astrophysics Data System (ADS)

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 asthenospheric mantle. The temperature at the base of the lithosphere is the parameter controlling the asthenosphere rising.

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

2013-04-01

31

Genetic features of petroleum systems in rift basins of eastern China  

USGS Publications Warehouse

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 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 oil source centre.

Qiang, J.; McCabe, P. J.

1998-01-01

32

Earthquakes along the East African Rift System: A multi-scale, continent-wide perspective  

NASA Astrophysics Data System (ADS)

Based on a comprehensive dataset of precisely determined depths of 121 large to moderate-sized earthquakes along and near the entire East African Rift system (EARS), there are three distinct patterns in focal depths which seem to reflect progressive stages in the development of the largest active rift in the world. First, away from both ends of the western, younger branch of the EARS, very large (MW ?7) earthquakes occurred in the top 15 km of the crust where surficial expressions of rifting are yet to appear. Curiously there are unusually deep aftershocks reaching down to 33±4 km. Second, under well-developed but amagmatic rift segments, focal depths show a bimodal distribution, with peaks centered near depths of about 15±5 km and 35±5 km. This pattern is present both under the main axis of the EARS where rift basins have lengths approaching 1,000 km, and beneath isolated rift segments ten times shorter in length. Underside reflections off the Moho indicate that at least part of the second peak in seismicity is due to mantle earthquakes down to 44±4 km, attesting to high differential stress in the mantle lithosphere which is capable of accumulating seismogenic elastic strains (the “jelly sandwich” rheology). Third, beneath magmatic segments of well-developed rifts, seismicity is largely confined to the upper 15 km of the crust, akin to the pattern along mid-ocean ridges where plastic flow due to high temperature inhibits accumulation of shear stress deep in the lithosphere.

Yang, Z.; Chen, W.

2009-12-01

33

The 1789 Rifting Event in the Hengill Volcanic System, SW-Iceland  

NASA Astrophysics Data System (ADS)

A volcano-tectonic episode in South Iceland in the 18th century was initiated by rifting and eruptions along the 30 km long Laki fissure within the Eastern Volcanic Zone (EVZ) and an eruption at the northern Reykjanes Reykjanes Ridge in 1783, forming the island of Nýey. Severe earthquakes within the South Iceland Seismic Zone (SISZ) followed in 1784. The sequence ended in 1789, with a rifting event in the Hengill volcanic system, located at the junction of the Western Volcanic Zone (WVZ) with the SISZ. The Hengill system consists of a central volcano, Mt. Hengill, which is transected by a 60 km long SW-NE striking rift zone. The rift north of Mt. Hengill forms a 6 km wide graben, partly filled with the lake Thingvallavatn. The central volcano is marked by high volcanic production, occurrences of acid rocks and a high temperature geothermal field. Rifting events within the Hengill system are considered to be mainly associated with crustal dike propagation as dikes have only breached the surface in an eruption four times during the Holocene. Extension rate is signified by tension gashes of about 70 m aggregate width across the rift zone in a 10,000 year old lava and by a maximum throw of about 40 m at Thingvellir near its western margin. In 1789, settlements only existed at the distal ends of the Hengill rift zone, at Selvogur and Thingvellir. A fairly detailed contemporary description of the rifting event exists, written by the vicar of Thingvellir. He states that the rifting 1789 began in early June and lasted 10 days with considerable earthquake activity. The central part of the Thingvellir graben subsided and the lake transgressed beyond its former shore while the margins of the graben were elevated so that water wells ran dry. Trails across the main boundary faults of Almannagjá and Hrafnagjá became impassable for horses. Old surface fissures widened and new formed. Fault movement was also observed southwest of lake Thingvallavatn, where a fault subsidence was reported being equal to a person in height, obviously considered rather spectacular for its size. There is mentioning of new hot springs having formed south of Mt. Hengill and a collapse of houses at the southwest end of the rift zone in Selvogur. A peat bog at the northeastern shore of the lake overlain by lake mud at 1.4-1.5 m depth indicates the amount of subsidence during the rifting event. A man-made rockwall submerged near the north shore of lake Thingvallavatn lies at a depth of 2.6 m, of which about 0,2 m are probably due to latent creep spanning the last 2 centuries. As there is no mentioning of subsequent events within the Hengill system, the 1789 rifting is considered a singular event consisting of dike propagation from the Hengill central volcano into both segments of the rift zone.

Saemundsson, K.

2006-12-01

34

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)

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 orientation, fault kinematics and block rotation (once in play) re-enforce each other, and depending on the local kinematics different parts of a captured block can be rotated by different amounts but in the same general direction. The results are compared with the natural scenario. Keywords: Albertine rift; Analogue; Extension; Kinematics; Transfer zone

Aanyu, Kevin; Koehn, Daniel

2010-05-01

35

MONITORING OF EARTHQUAKES ACTIVITIES ALONG THE SYRIAN RIFT SYSTEM ( LEFT-LATERAL) BY USING REMOTE SENSING AND GIS DATABASE  

Microsoft Academic Search

Northwest of Syria 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 rift system (Left-Lateral or African- Syrian Rift System). Those areas are tectonically active and caused a lot of seismically events. The AL-Ghab Graben complex is situated within this wide area

MOUTAZ DALATI

36

Internal structure and evolution of a volcanic rift system in the eastern North Atlantic: the Desertas rift zone, Madeira archipelago  

Microsoft Academic Search

The three elongated Desertas Islands form the top of a 60-km-long NW–SE-striking submarine ridge southeast of Madeira (NE Atlantic). The alignment of eruptive centres and parallel dyke swarms indicates that the islands represent a deeply eroded volcanic rift zone. Detailed field studies combined with 40Ar\\/39Ar age determinations and geochemical analyses reveal the internal structure and evolution of this rift, which

Stefanie Schwarz; Andreas Klügel; Paul van den Bogaard; Jörg Geldmacher

2005-01-01

37

Normal Fault System of the Western Corinth Rift (Greece): 3D Geometry, Kinematics and Evolution  

NASA Astrophysics Data System (ADS)

We use an integrated approach from field analyses (stratigraphy, structural geology, seismicity) to 3D geomodelling of the Corinth rift to characterize the initiation and early stages of continental rifting. The Gulf of Corinth is a rapidly opening rift superimposed on the external Hellenides orogenic belt and lying above an active subduction zone. The early Corinth rift is today uplifted and spectacularly exposed along the southern margin of the Gulf. The Plio-Pleistocene syn-rift stratigraphy and normal fault system have been mapped across an area of 600 km2. Major normal faults are planar and have a low level of connectivity. Rare listric intra-basinal faults are observed. Fault strikes vary from N070° to N120° with an average strike of N110°. Fault dips, predominantly toward the north, vary from 45° to 65°. Extension directions vary from N355° to N020°. Total extension across the whole rift (offshore and onshore) is estimated to be 10km (b=1.2). Fault activity and depocentres migrated north with time as the rift narrowed. Syn-rift stratigraphy records three phases of rifting. Extension accelerated significantly at around 1.4 Ma and around 800-600 ka. Uplift of the south flank started sometime 800-600 ka. Field data alone are not sufficient to constrain a valid 3D model of geometry and displacement distribution on the normal fault network, in particular because of their irregular and often sparse distribution. 3D model construction therefore requires the integration of theoretical assumptions, in particular, (1) a coherent distribution of displacement across the fault network, (2) an acceptable ratio of displacement to fault length, (3) a consistent level of connectivity. In the initial onland model, faults surfaces are extended to a depth of 2 km. In contrast, the surface trace of active fault surfaces can be linked with earthquake nodal planes located at depths of 5-8 km depth. These models suggest that the north dipping zone of micro-seismicity in the western Gulf may not represent a extensional decollement zone.

Ford, M.; Le Carlier de Veslud, C.; Lyon-Caen, H.; Rohais, S.; Moullard, M.; Williams, E. A.

2008-12-01

38

Stratigraphy, Structure, and Ore Deposits of the Southern Limb of the Midcontinent Rift System  

NSDL National Science Digital Library

This site features an overview of the Midcontinent Rift system of North America, an area that extends for more than 2000 km northeasterly from Kansas, through the Lake Superior region, and then southeasterly through lower Michigan. This summary of the stratigraphy, structure, and mineralization of rift rocks provides an overview of the geologic history in northern Wisconsin and upper Michigan. Separate sections describe the tectonic history and structural features of the area, the stratigraphy of volcanic and sedimentary deposits, and the mineralization that produced rich copper and silver deposits. Information is supported by numerous citations while maps and diagrams help illustrate the concepts.

Bornhorst, T.; Woodruff, L.; Nicholson, S.; University, Michigan T.

39

Evaluation of volume of deep mantle outgassing during rifting. Final report, September 1987-February 1989  

SciTech Connect

It has been proposed that the major source of natural gas accumulations is inorganic methane outgassed from the mantle. However, for mantle methane to be incorporated into explorable hydrocarbon reservoirs, it must be transported upwards to the near-surface. Volatiles are strongly partitioned into melt phases and can be carried to the near surface by melts. Extensional rifts are sites of mantle partial melting, and thus perspective sites for outflow of mantle methane. The large-scale breaching of the lithosphere that occurs during rifting is a primary conduit for flow of deep mantle volatiles. Non-extension structures that do not breach the lithosphere and are non-volcanic, such as the Siljan ring, are unlikely to contain significant methane. However, not all continental extension leads to mantle melting. Rifts, such as the hydrocarbon-rich Gulf of Suez, that have had no significant mantle melting are unlikely to contain abiogenic hydrocarbons. To get significant mantle melt and volatile transport requires large extensional strain in localized areas, creating asthenospheric upwelling sufficient to induce decompression melting. There could be and probably are large volumes of methane liberated from some continental rifts where there has been melting.

Buck, W.R.; Steckler, M.S.

1991-03-01

40

Evaluation of volume of deep mantle outgassing during rifting. Final report, September 1987February 1989  

Microsoft Academic Search

It has been proposed that the major source of natural gas accumulations is inorganic methane outgassed from the mantle. However, for mantle methane to be incorporated into explorable hydrocarbon reservoirs, it must be transported upwards to the near-surface. Volatiles are strongly partitioned into melt phases and can be carried to the near surface by melts. Extensional rifts are sites of

W. R. Buck; M. S. Steckler

1991-01-01

41

Tectonic development of the SW Arabian Plate margin within the central Arabian flank of the Red Sea rift system  

NASA Astrophysics Data System (ADS)

The Red Sea rift system is a prime example of continental rifting and has contributed significantly to our understanding of the geologic processes that manage the rupture of continental lithosphere. Using a combined geo- and thermochronometric approach, we explore the modes and mechanisms of rift margin development by studying Red Sea rift-related geologic products along the central Saudi Arabian flank of the rift system, north of Jeddah. We use apatite and zircon (U-Th)/He thermochronometry and whole-rock 40Ar/39Ar dating of basalt to define the spatiotemporal relationship between rift flank extensional structures and rift-related harrat volcanism. This technical approach permits the reconstruction of the tectonic margin from early rift architecture, to strain distribution during progressive rifting, and through subsequent whole-scale modifications of the rift flank due to thermal and isostatic factors. Constraints on the dynamics of rift flank deformation are achieved through the collection of geologic samples along long-baseline thermochronometric transects that traverse the entire Arabian shield from the coastal escarpment to the inland Paleozoic sedimentary cover sequences. Long-baseline transects resolve the timing of rift flank uplift and reveal the pattern of lithospheric modification during the rupturing of continental lithosphere. Locally, short-baseline elevation transects map the footwall exhumation of major normal faults that delineate both the modern rift margin and inland extensional basins such as the NW-trending Hamd-Jizil basin, a prominent syn-extensional basin comprised of two distinct half-grabens (Jizil and Hamd) located NW of Medina. Diffuse lithospheric extension during the Oligo-Miocene affected a widespread area well inboard from the modern rift margin; samples from footwall blocks that bound the inland Jizil and Hamd half-grabens yield apatite (U-Th)/He cooling ages of 14.7 ± 0.9 Ma and 24.5 ± 1.5 Ma, respectively. The mid-Miocene age is doubly-significant since it reveals not only a Red Sea rift signal 140 km inboard from the modern border fault complex but also underscores the importance of fault reactivation during progressive rifting since the Jizil half-graben is structurally delineated by faults formed within the Neoproterozoic Najd shear zone fabric. Oligo-Miocene apatite (U-Th)/He ages from Jabal Radwa, a pluton exhumed within the border fault complex, show that rift flank exhumation and extensional faulting occurred within the central portion of the Arabian rift flank penecontemporaneous to faulting in the Hamd-Jizil half-graben system. Within the rift flank fault systems, an absence of footwall exhumation ages younger than ~13 Ma confirms that major extensional faulting migrated basin-ward in the middle Miocene during a time of rift reorganization and the establishment of the Dead Sea-Gulf of Aqaba transform. However, minor deepening of the inland Hamd-Jizil basin continued through the late Miocene as relatively young, basin-internal faults cut 17 Ma - 10 Ma basalt flows from harrat Khaybar that had blanketed the region.

Szymanski, E.; Stockli, D. F.; Johnson, P. R.; Kattan, F. H.; Cosca, M. A.

2009-12-01

42

Morphotectonic evolution of two depressions at the southern border of the Baikal rift system  

NASA Astrophysics Data System (ADS)

Detailed study of two dry depressions in the Baikal rift system: the E W Khoito Ghol-Tunka-Bistraya depression and the SW NE Gusinoje Ivolga depression, aims to provide a better understanding of tectonic control on the intershoulder relief evolution after the rift opened. Both depressions are grabens and both feature a suite of 10 20 km-wide basins alternating with more or less massive highs. Field and laboratory analysis shows that this pattern is of recent tectonic origin and that local breaking-up and subsidence followed the general sinking which originally formed the grabens. The subsidence belts seem to have gradually shifted north and northeastwards. Geomorphological analysis reveals that in both depressions the highs are remnants of a former pediment which was broken up. The young basins display numerous relevant hydrographic anomalies of the secondary channels and a general water-logging. They also suggest that the subsidence belts have gradually shifted north-and northeastwards. In the Gusinoje Ivolga depression evidence was found of a Plio-Pleistocene river course, parallel to the Selenga river, which was later dismantled by the breaking-up. This depression, parallel to the Baikal rift and belonging to the Mesozoic system of grabens in the Caledonian fold belt, seems to have been included into the general system of rifts during the Pliocene tectonic phase. As for the main hydrographic axes, the Selenga river was set on a Palaeogene-age planation surface before the first tectonic phase and kept its original course. The Irkut river flowed in the Khoito Gol Tunka Bistraya depression after the first tectonic phase and was not affected by the later breaking-up. In contrast, the secondary drainage network is largely discordant. Despite their different geotectonic contexts, the two depressions show a similar development of relief pattern,which poses the question of the style of rift dynamics after the main Pliocene tectonic phase.

Vogt, Henri; Vogt, Thea

2007-05-01

43

Mapping hyper-extended rift systems offshore and onshore: insights from the Bay of Biscay- Western Pyrenees  

NASA Astrophysics Data System (ADS)

Research conducted at present-day passive continental margins shows more varied crustal architectures than previously assumed. New seismic data together with drill-holes have revealed the occurrence of extremely thinned continental crust in the distal part of the margin as well as exhumed serpentinised sub-continental mantle oceanwards. In addition the understanding of the formation of hyper-extended rift systems has also greatly benefited from the study of onshore analogs preserved in mountain belts. The Bay of Biscay and Western Pyrenees correspond to a Lower Cretaceous rift system leading to the development of hyper-extended domains and ultimately oceanic crust in the Bay of Biscay. This domain represents one of the best natural laboratories to study the formation processes and evolution of hyper-extended domains. During late Cretaceous compression, these rifted domains were inverted resulting in the present-day Pyrenean mountain belt. In this contribution, we present a new paleogeographic map of the Bay of Biscay-Pyrenean rift system. We integrate results from previous works and new work using different mapping methods to distinguish distinctive crustal domains related to hyper-extended systems both offshore and onshore. We combine seismic interpretations with gravity anomaly inversion and residual depth anomaly analysis to distinguish the different crustal domains across the offshore margin. Onshore, we use an innovative approach based on observations from present-day rifted margin architecture associated with classical field work to map the former hyper-extended domains. Another outcome of this work is the creation of a crustal thickness map using gravity inversion linking offshore and onshore domains from the Bay of Biscay to that of the Western-Pyrenees. This multidisciplinary approach enables us to investigate the spatial and temporal evolution of the Bay of Biscay rift system with the aim of better understanding the formation of hyper-extended domains. Results from both the interpretation of Bay of Biscay rift system and of the crustal thickness map suggest that (1) the spatial evolution of the hyper-extended rift system is more complex than previously assumed and (2) the rift system is strongly segmented at different scales by inherited transfer faults and shear zones bounding different rift basins (e.g. the Pamplona fault, onshore) or delimiting major changes of architecture (e.g. the South Armorican Shear Zone, offshore). Through this work, we aim to illustrate and investigate the processes related to the formation the Bay of Biscay-Western Pyrenees rift system. Moreover, the mapping methods used in this study may be applied to better understand other hyper-extended rift systems.

Tugend, Julie; Manatschal, Gianreto; Kusznir, Nicolas J.; Masini, Emmanuel; Thinon, Isabelle

2013-04-01

44

Two mantle plumes beneath the East African rift system: Sr, Nd and Pb isotope evidence from Kenya Rift basalts  

Microsoft Academic Search

Major and trace element and radiogenic isotope ratios (Sr, Nd and Pb) are presented for a suite of Neogene to Recent basalts (MgO>4 wt%) from the axial regions of the Kenya Rift. Samples have compositions ranging from hypersthene-normative basalt through alkali basalt to basanite and are a subset of a larger database in which compositions extend to nephelinite. A broadly

Nick Rogers; Ray Macdonald; J. Godfrey Fitton; Rhiannon George; Martin Smith; Barbara Barreiro

2000-01-01

45

Transect across the West Antarctic rift system in the Ross Sea, Antarctica  

USGS Publications Warehouse

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 rift system. 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-rift 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 rift system, with greatest extension beneath the early-rift grabens. The large amount of crustal stretching below the major rift basins may reflect the existence of deep crustal suture zones which initiated in an early stage of the rifting, 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 relatively small extension, concentrated in the western half of the Ross Sea, during Cenozoic time.

Trey, H.; Cooper, A. K.; Pellis, G.; Della, Vedova, B.; Cochrane, G.; Brancolini, G.; Makris, J.

1999-01-01

46

Sismotectonics in the western branch of the East African Rift System  

NASA Astrophysics Data System (ADS)

The western branch of the East African rift system 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 rift system, in DRC, Rwanda, Burundi and Tanzania. Neotectonic activity related to the western rift branch is in general well expressed and relatively well studied in the eastern flank of this rift branch, in Uganda, Rwanda, Burundi and Tanzania. In contrast, the western flank of this rift 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 rift 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. Therefore, this compilation will highlight the pattern of neotectonic faults (those active since the onset of the last and currently active tectonic stage) rather than those of active faults (with proven activity during the last 10 Ka). The first- and second-order stress field of this region is relatively well known thanks to the stress inversion of earthquake focal mechanisms, but the more detailed stress field related to the interaction of fault segments has still to be defined.

Delvaux, Damien; Kervyn, François; Mulumba, Jean-Luc; Kipata, Louis; Sebagenzi, Stanislas; Mavonga, Georges; Macheyeki, Athanas; Temu, Elly Bryan

2013-04-01

47

The Mercedario rift system in the principal Cordillera of Argentina and Chile (32° SL)  

Microsoft Academic Search

Recent studies carried out in the High Andes of central-western Argentina in the provinces of San Juan and Mendoza have established its stratigraphic and structural evolution. This paper presents new data on the Triassic–Early Jurassic rift system, the depositional sequences, and a synthesis of the tectonic evolution of the region, along with a correlation with the Chilean continental margin.The paleogeographic

P. Pamela Alvarez; Victor A. Ramos

1999-01-01

48

The transition from diffuse to focused extension: Modeled evolution of the West Antarctic Rift system  

NASA Astrophysics Data System (ADS)

Two distinct stages of extension are recognized in the West Antarctic Rift system (WARS). During the first stage, beginning in the Late Cretaceous, extension was broadly distributed throughout much of West Antarctica. A second stage of extension in the late Paleogene was focused primarily in the Victoria Land Basin, near the boundary with the East Antarctic craton. The transition to focused extension was roughly coeval with volcanic activity and strike slip faulting in the adjacent Transantarctic Mountains. This spatial and temporal correspondence suggests that the transition in extensional style could be the result of a change in plate motions or impingement of a plume. Here we use finite element models to study the processes and conditions responsible for the two-stage evolution of rifting in the WARS. Model results indicate that the transition from a prolonged period of broadly distributed extension to a later period of focused rifting did not require a change in the regional stress regime (changes in plate motion), or deep mantle thermal state (impingement of a plume). Instead, we attribute the transition from diffuse to focused extension to an early stage dominated by the initially weak accreted lithosphere of West Antarctica, and a later stage that concentrated around a secondary weakness located at the boundary between the juvenile West Antarctica lithosphere and Precambrian East Antarctic craton. The modeled transition in extension from the initially weak West Antarctica region to the secondary weakness at the West Antarctic East Antarctic boundary is precipitated by strengthening of the West Antarctica lithosphere during syn-extensional thinning and cooling. The modeled syn-extensional strengthening of the WARS lithosphere promotes a wide-rift mode of extension between 105 and ˜ 65 Ma. By ˜ 65 Ma most of the extending WARS region becomes stronger than the area immediately adjacent to the East Antarctic craton and extension becomes concentrated near the East Antarctic/West Antarctic boundary, forming the Victoria Land Basin region. Mantle necking in this region leads to syn-extensional weakening that promotes a narrow-rift mode of extension that becomes progressively more focused with time, resulting in formation of the Terror Rift in the western Victoria Land Basin. The geodynamic models demonstrate that the transition from diffuse to focused extension occurs only under a limited set of initial and boundary conditions, and is particularly sensitive to the pre-rift thermal state of the crust and upper mantle. Models that predict diffuse extension in West Antarctica followed by localization of rifting near the boundary between East and West Antarctica require upper mantle temperatures of 730 ± 50 °C and sufficient concentration of heat producing elements in the crust to account for ˜ 50% of the upper mantle temperature. Models with upper mantle temperatures < ca. 680 °C and/or less crustal heat production initially undergo diffuse extension in West Antarctica, and quickly develop a lithospheric neck at the model edge furthest from East Antarctica. Models with upper mantle temperatures > ca. 780 °C do not develop focused rifts, and predict indefinite diffuse extension in West Antarctica.

Huerta, Audrey D.; Harry, Dennis L.

2007-03-01

49

Thermal and exhumation history of the central Rwenzori Mountains, Western Rift of the East African Rift System, Uganda  

Microsoft Academic Search

The Rwenzori Mountains (Mtns) in west Uganda are the highest rift mountains on Earth and rise to more than 5,000 m. We apply\\u000a low-temperature thermochronology (apatite fission-track (AFT) and apatite (U–Th–Sm)\\/He (AHe) analysis) for tracking the cooling\\u000a history of the Rwenzori Mtns. Samples from the central and northern Rwenzoris reveal AFT ages between 195.0 (±8.4) Ma and\\u000a 85.3 (±5.3) Ma, and

F. U. Bauer; U. A. Glasmacher; U. Ring; A. Schumann; B. Nagudi

2010-01-01

50

Structure and geochronology of the southern Xainza-Dinggye rift and its relationship to the south Tibetan detachment system  

NASA Astrophysics Data System (ADS)

The Xainza-Dinggye rift is one of several north-south trending rifts in central and southern Tibet created by Cenozoic east-west extension during Indo-Asian convergence. The southern part of the rift cuts through the Tethyan and High Himalayas. In the Tethyan Himalaya, this rift 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 rift 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 system (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 rift is younger than the STDS because it offsets the STDS; this north-south trending rift belongs to a different tectonic system 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 rift may indicate an important change in tectonic regime at ˜13 Ma in the building of the plateau.

Zhang, Jinjiang; Guo, Lei

2007-03-01

51

Thermochronological investigation of the timing of rifting and rift segmentation in the Gulf of Suez, Egypt  

Microsoft Academic Search

The Tertiary Gulf of Suez rift system is one of the best-studied continental rift systems and has inspired many fundamental geodynamic models for continental rifting. 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 rift. A critical aspect of constraining the evolution

W. Bosworth; D. F. Stockli

2006-01-01

52

The distribution of basaltic volcanism on Tenerife, Canary Islands: Implications on the origin and dynamics of the rift systems  

NASA Astrophysics Data System (ADS)

One of the most characteristic features of volcanic islands is the existence of rift zones defined commonly as orientated eruptive fissures or parallel rows of elongate cinder cones and dyke swarms. Occasionally, these rifts can appear at the birth of the volcanic island and persist until the last episodes of its constructions, controlling the form and structure of the island (e.g. Azores Islands). In the case of Tenerife (Canary Islands), it is possible to observe two rift zones (Santiago del Teide and Dorsal rifts) running NW-SE and ENE-WSW, marked by parallel rows of aligned cones and eruptive fissures. Additionally, at the southern part of the island (Southern Volcanic Zone) basaltic volcanism is characterized by scattered vents and apparently non-coherently orientated eruptive fissures. Some authors relate the existence of the latter volcanism to a N-S running rift zone that defines the third branch of a three-armed rift system in the island. In the present paper, we first investigate the tectonic controls on the distribution of basaltic volcanism at the Southern Volcanic Zone, and their relation with the NW-SE and ENE-WSW rifts. The numerical results obtained suggest that basaltic volcanism of the southern part of Tenerife can be easily explained as the result of a extensional stress field derived from the combined effects of the NW-SE and ENE-WSW rifts. As a second objective, we have also investigated the origin of the Santiago del Teide and Dorsal rift zones and their role on the formation of the original shield volcano and the subsequent evolution of the whole island. Our numerical results contrast with previously published explanations on the origin of the Tenerife rifts that included fracturing due to volcano spreading or to deformation of the volcano due to magma intrusion. We consider that volcanic activity in Tenerife began throughout fissural volcanism along these structures that were already present in the oceanic basement, progressively accumulating the basaltic series that gave rise to the construction of the composite shield volcano.

Geyer, A.; Martí, J.

2010-03-01

53

Evolution Of The West Antarctic Rift System And the Importance of Crustal Heat Production  

NASA Astrophysics Data System (ADS)

Two distinct stages of extension are recognized in the West Antarctic Rift system (WARS). During the first stage in the Late Cretaceous through middle Paleogene Periods extension was broadly distributed throughout most of the Ross Sea region. Later, during the Late Paleogene and younger, the style of extension changed and was focused primarily in the Terror Rift, near the boundary with the East Antarctic craton. We have developed a finite element model to study the processes and conditions responsible for this two-stage evolution of rifting. Model results consistent with the geologic history of the WARS indicate that the transition from a period of broadly distributed extension to a later period of strongly focused rifting can evolve naturally without requiring a change in either the regional stress regime or thermal state. No change in plate motion directions or rates or changes in the mantle thermal state (impingement of a plume) are required. The initial stage of modeled diffuse extension throughout West Antarctica results from a prescribed uniformly weak West Antarctic lithosphere (thinner, hotter) versus a prescribed stronger East Antarctic lithosphere (thicker, colder). The transition from diffuse to focused extension under constant regional stress and thermal conditions occurs only under a limited set of initial thermal conditions. Simulations that have an initial West Antarctic thermal structure with significant heat from the crust result in a lithosphere that strengthens as it thins. This strengthening is due to the cooling of the upper mantle as the thickness of the crust is reduced (thus the total heat generated in the crust is reduced). As a subset of this class of simulations, instances in which the initial East Antarctic crust generates moderately high amounts of heat result in a focusing of extension near the boundary between East and West Antarctica. This focusing is due to the relative weakness of the upper mantle near the East/West Antarctic boundary due to heat conducted from the warm East Antarctic crust. Thus, crustal heat production can play an important role in controlling the deformational evolution of extensional systems.

Huerta, A. D.; Harry, D. L.

2004-12-01

54

Continental rifts and mineral resources  

SciTech Connect

Continental rifts are widespread and range in age from the present to 3 b.y. Individual rifts may form parts of complex systems as in E. Africa and the Basin and Range. Rifts 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 rift 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). Rift volcanics are linked to local hydrothermal systems and to extensive zeolite deposits (Basin and Range, East Africa). Copper (Zambia, Belt), zinc (Red Dog) and lead ores (Benue) are related to hydrothermal systems which involve hot rock and water flow through both pre-rift basement and sedimentary and volcanic rift fill. Economically significant sediments in rifts 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 rifts relate to a variety of source, reservoir and trap relations (North Sea, Libya), but rift-lake sediment sources are important (Sung Liao, Bo Hai, Mina, Cabinda). Some ancient iron ores (Hammersley) may have formed in rift 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 rifted crests (Ecuador, N. Peru). The Pongola, on Kaapvaal craton may, on the other hand represent the world's oldest preserved, little deformed, continental rift.

Burke, K. (Univ. of Houston, TX (United States). Geosciences Dept.)

1992-01-01

55

A gravity link between the domally uplifted Cainozoic volcanic centres of North Africa and its similarity to the East African Rift System anomaly  

Microsoft Academic Search

Attention is drawn to the existence of a negative gravity lineament linking the domally uplifted Cainozoic volcanic centres of North and West Africa to the negative Bouguer anomaly associated with the East African Rift System. The gravity lineament is shown to have similar dimensions to the Rift System anomaly and is interpreted as resulting from attenuation of the continental lithosphere.

J. D. Fairhead

1979-01-01

56

Prebreakup geology of the Gulf of Mexico-Caribbean: Its relation to Triassic and Jurassic rift systems of the region  

NASA Astrophysics Data System (ADS)

A review of the prebreakup geology of west central Pangea, comprising northern South America, the Gulf of Mexico, and West Africa, combined with a study of the Mesozoic rift trends of the region confirms a relation between the rift systems and the underlying older grain of deformation. The prebreakup 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 west central Pangea. Along the northern South American margin and Yucatan a paleo northeast trending Pan-African aged fold belt is documented. A second system is observed along West Africa extending from the High Atlas to the Mauritanides and Rockelides. Similar aged orogenies in the Appalachians are compared. 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 system is northeast-southwest and essentially parallels the Guayana craton and West African and eastern North American cratons. Mesozoic rifling closely followed either the Precambrian trends or the late Paleozoic orogenic belt. The Triassic component focused along the western portions of the Gulf of Mexico continuing into eastern Mexico and western South America. The Jurassic rift trend followed along the separation between Yucatan and northern South America. At Lake Maracaibo the Jurassic rift system eventually overlaps the Triassic rifts. The Jurassic rift resulted in the "Hispanic Corridor" that permitted Tethyan and Pacific marine faunas to mix at a time when the Gulf of Mexico underwent continental sedimentation.

Bartok, Peter

1993-01-01

57

Probing the processes and products of an ancient continental crustal rupture: Scientific drillng into the Midcontinent Rift System  

Microsoft Academic Search

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 Rift (MCR) System of North America are particularly attractive for studying subcontinental

Hinz

1988-01-01

58

Usually deep earthquakes in East Africa: Constraints on the thermo-mechanical structure of a continental rift system  

Microsoft Academic Search

Shudofsky [1985] has established that earthquakes associated with the East African rift system have well-constrained focal depths as great as 25-30 km. Using published heat flow measurements as a guide to the local geotherm, we find through simple stress envelope calculations that the deepest earthquakes probably occur in the lower crust in a region where the lithosphere is strong. These

Gordon N. Shudofsky; Sierd Cloetingh; Rinus Wortel; Seth Stein

1987-01-01

59

Active deformation of the Corinth rift, Greece: Results from repeated Global Positioning System surveys between 1990 and 1995  

Microsoft Academic Search

Between 1990 and 1995, we carried out seven Global Positioning System (GPS) campaigns in the Corinth rift area in order to constrain the spatial and temporal crustal deformation of this active zone. The network, 193 points over ~10,000 km2, samples most of the active faults. In order to estimate the deformation over a longer period, 159 of those points are

P. Briole; A. Rigo; H. Lyon-Caen; J. C. Ruegg; K. Papazissi; C. Mitsakaki; A. Balodimou; G. Veis; D. Hatzfeld; A. Deschamps

2000-01-01

60

East African Rift System (EARS) Plume Structure: Insights from Quaternary Mafic Lavas of Turkana, Kenya  

Microsoft Academic Search

Quaternary mafic lavas from Lake Turkana (northern Kenya) provide information on processes operating beneath the East African Rift in an area of anomalous lithospheric and crustal thinning. Inferred depths of melting beneath Turkana (15---20km) are shal- lower than those recorded elsewhere along the rift, consistent with the anomalously thin crustal section. The mafic lavas have elevated incompatible trace element contents

TANYA FURMAN; JULIA G. BRYCE; JEFFREY KARSON; ANNAMARIA IOTTI

2004-01-01

61

Formation of the double rift system in the Thaumasia Highlands, Mars  

NASA Astrophysics Data System (ADS)

The Thaumasia Highland Rifts are two complex graben structures in the Thaumasia Highland belt, located in the southern Thaumasia region, Mars. The rifts are arranged 90-130 km apart in a nearly subparallel setting and represent a very unusual style of crustal deformation. We have investigated the mechanism responsible for this peculiar style of rifting and found strain localization by volcanic weak zones to be a major factor for fault-pattern formation, indicating widespread prerift and synrift volcanic activity in the region. This result is consistent with the high heat flow during rift emplacement as estimated from rift flank uplift. Our results indicate that the onset of volcanism predates the rift formation process and that magmatism and the associated lithospheric weak zones control the rift locations. The simulations performed here are in good agreement with the observations for extension in the NW-SE to NNW-SSE direction, and we favor a formation scenario involving passive rifting in a magmatectonically active environment.

Grott, M.; Kronberg, P.; Hauber, E.; Cailleau, B.

2007-06-01

62

Kinematics of the South Atlantic rift  

NASA Astrophysics Data System (ADS)

The South Atlantic rift basin evolved as branch of a large Jurassic-Cretaceous intraplate rift zone between the African and South American plates during the final breakup of western Gondwana. While the relative motions between South America and Africa for post-breakup times are well resolved, many issues pertaining to the fit reconstruction and particular the relation between kinematics and lithosphere dynamics during pre-breakup remain unclear in currently published plate models. We have compiled and assimilated data from these intraplated rifts and constructed a revised plate kinematic model for the pre-breakup evolution of the South Atlantic. Based on structural restoration of the conjugate South Atlantic margins and intracontinental rift basins in Africa and South America, we achieve a tight fit reconstruction which eliminates the need for previously inferred large intracontinental shear zones, in particular in Patagonian South America. By quantitatively accounting for crustal deformation in the Central and West African rift zone, we have been able to indirectly construct the kinematic history of the pre-breakup evolution of the conjugate West African-Brazilian margins. Our model suggests a causal link between changes in extension direction and velocity during continental extension and the generation of marginal structures such as the enigmatic Pre-salt sag basin and the São Paulo High. We model an initial E-W directed extension between South America and Africa (fixed in present-day position) at very low extensional velocities until Upper Hauterivian times (?126 Ma) when rift activity along in the equatorial Atlantic domain started to increase significantly. During this initial ?17 Myr-long stretching episode the Pre-salt basin width on the conjugate Brazilian and West African margins is generated. An intermediate stage between 126.57 Ma and Base Aptian is characterised by strain localisation, rapid lithospheric weakening in the equatorial Atlantic domain, resulting in both progressively increasing extensional velocities as well as a significant rotation of the extension direction to NE-SW. From Base Aptian onwards diachronous lithospheric breakup occurred along the central South Atlantic rift, first in the Sergipe-Alagoas/Rio Muni margin segment in the northernmost South Atlantic. Final breakup between South America and Africa occurred in the conjugate Santos-Benguela margin segment at around 113 Ma and in the Equatorial Atlantic domain between the Ghanaian Ridge and the Piauí-Ceará margin at 103 Ma. We conclude that such a multi-velocity, multi-directional rift history exerts primary control on the evolution of this conjugate passive margins systems and can explain the first order tectonic structures along the South Atlantic and possibly other passive margins.

Heine, C.; Zoethout, J.; Müller, R. D.

2013-01-01

63

Evolution of Rifting in Africa  

Microsoft Academic Search

THE recent report by Girdler et al.1 on the rift system of East Africa is of great interest because it presents a crustal model, based on new gravity observations, which suggests an intrusion of low velocity mantle material rising to the base of the sialic crust which underlies the eastern and western rift valleys of East Africa between 3° N

R. B. McConnell

1970-01-01

64

Geophysical diagnosis of MidContinent rift  

Microsoft Academic Search

Of all recognized rift systems, the Mid-Continent rift may be the most geophysically analyzed of its genre. The data base associated with this 1900-km (1180-mi) long plate tectonic feature is evenly distributed between gravity, magnetics, and seismology. Since 1983, the western arm of the rift, traced from northeastern Kansas into the Lake Superior basin, has become an oil and gas

Dickas

1986-01-01

65

Factors controlling depth of continental rifts  

NASA Astrophysics Data System (ADS)

Rifting is a fundamental plate tectonic process, which forms elongated, narrow tectonic depressions in the Earth's surface and, eventually, may break continental plates to form new oceanic lithosphere. Subsidence of rift basins is caused by thinning of the crust and lithospheric mantle together with isostatic compensation for the extra load of sediments and thermal relaxation. It is generally believed that the final depth of rift basins is primarily controlled by the amount of stretching and that other processes only have secondary influence. However, we show that the relative rheological strength of faults inside and outside rift zones exerts substantial control on the volume of the final rift basin (by more than a factor of 3) even for the same amount of extension (total or inside the rift zone). This surprising result is mainly caused by irreversible deepening of the rift graben during stretching due to lower crustal flow when the faults in the rift zone are weak, whereas the effect is negligible for strong faults. Relatively strong faults inside the rift zone lead to substantial stretching of adjacent crust, and we find that long term stretching outside the main rift zone may explain the formation of wide continental margins, which are now below sea level. We also demonstrate that fast syn-rift erosion/sedimentation rates can increase the final volume of rift basins by up to a factor of 1.7 for weak crustal faults, whereas this effect is insignificant for strong faults inside the rift zone. These findings have significant implications for estimation of stretching factors, tectonic forces, and geodynamic evolution of sedimentary basins around failed rift zones.

Elesin, Y.; Artemieva, I. M.; Thybo, H.

2011-12-01

66

Jordan Rift Valley Development Symposium: Final Report. Held in Amman, Jordan on April 24-26, 1995.  

National Technical Information Service (NTIS)

The study, conducted by CORE International, was funded by the U.S. Trade and Development Agency. The report was prepared for the Jordan Rift Valley Development Symposium held in Amman, Jordan. The report shows the technical areas covered during the sympos...

V. K. Shrivastava L. Shrivastava L. Varrick

1995-01-01

67

Structural style of the Turkana Rift, Kenya  

SciTech Connect

Multifold seismic reflection and geologic mapping in part of the eastern branch of the East African Rift system of northern Kenya reveal a major rift structure containing at least 3 km of Neogene sediment fill beneath Lake Turkana. This includes a series of half-graben basins, with centrally located quaternary volcanic centers, which are linked end-to-end by structural accommodation zones. Whereas the geometry of rifting is similar to that of the nonvolcanic western branch of the East African Rift system, the Turkana half-grabens are much smaller and may reflect extension of a thinner lithosphere or development of more closely spaced fracture patterns during rift evolution, or both.

Dunkelman, T.J.; Karson, J.A.; Rosendahl, B.R.

1988-03-01

68

How many rifts are there in West Africa?  

Microsoft Academic Search

The West African Rift System has, for the last ten years, been thought to consist of five interconnected rifts 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 rifts in West Africa; the Lower Benue Rift which extends to the northeast

S. J. Freeth

1984-01-01

69

New Insights into the Transition From Magmatic to Tectonic Rifting  

Microsoft Academic Search

Magma plays a major role in the development of many rifts and continental margins. This is particularly clear for some of the more recent continental rifts including the Afro-Arabian Rift System and the breakup of South America from Africa. We are interested in how magma, injected as dikes, may lead to weakening of the lithosphere so that rifting can proceed

R. W. Bialas; W. R. Buck; R. Qin

2008-01-01

70

Rift Valley Fever Virus Nonstructural Protein NSs Promotes Viral RNA Replication and Transcription in a Minigenome System  

Microsoft Academic Search

Rift Valley fever virus (RVFV), which belongs to the genus Phlebovirus, family Bunyaviridae, has a tripartite negative-strand genome (S, M, and L segments) and is an important mosquito-borne pathogen for domestic animals and humans. We established an RVFV T7 RNA polymerase-driven minigenome system in which T7 RNA polymerase from an expression plasmid drove expression of RNA transcripts for viral proteins

Tetsuro Ikegami; C. J. Peters; Shinji Makino

2005-01-01

71

Extension of the southeastern terminus of the Midcontinent Rift System southward from Michigan to the Ohio-Kentucky border  

Microsoft Academic Search

The Midcontinent Rift System (MRS), a 2,700 km long, horseshoe shaped, intra-continental, thermo-tectonic structure of Middle Proterozoic age, extends from central Kansas to at least southern Ohio by way of the Lake Superior basin. Its western arm, geophysically identified as the Midcontinent Gravity High, has recently been clarified structurally and lithologically as a result of extensive seismic reflection surveying and

Dickas

1992-01-01

72

Transition From a Magmatic to a Tectonic Rift System : Seismotectonics of the Eyasi- Manyara Region, Northern Tanzania, East Africa  

NASA Astrophysics Data System (ADS)

How a rift system propagates and breaks throughout a cold and thick continental crust remains poorly known. Only few places allow to address the question. In the East African Rift System (EARS), the eastern magma- rich branch abruptly splits into two amagmatic arms (the Eyasi and Manyara faulted systems), south of a E-W volcanic chain (the Ngorongoro-Kilimanjaro transverse volcanic belt), as crossing the Archaean Tanzanian craton margin. We present the first detailed seismotectonic picture of the Eyasi-Manyara rifts where a network of ~25 seismometers was settled from June to November 2007 (SEISMO-TANZ'07 seismological experiment). From the seismicity recorded by the network, we identify active faults and discuss the stress field framework obtained from the inversion of focal mechanisms. We use the determined depth of earthquakes (1) to discuss the crustal structure of the transition zone from a magma-rich to a magma-starved section of the EARS and (2) to further emphasize the rheological control on depth distributions in the EARS (Albaric et al., Tectonophysics, 2008). The stress and strain directions deduced from our work are also used to question recently published kinematics and conceptual models of the EARS (Calais et al., Geol. Soc. London, 2006 ; Le Gall et al., Tectonophysics, 2008).

Albaric, J.; Perrot, J.; Deschamps, A.; Deverchere, J.; Wambura, R. F.; Tiberi, C.; Petit, C.; Le Gall, B.; Sue, C.

2008-12-01

73

Anatomy of a rift system: Triassic-Jurassic basins of eastern North America  

SciTech Connect

Basins containing the early Mesozoic Newark Supergroup formed during the incipient rifting of Pangaea. The basins are characterized by the following: (1) The border fault systems (BFS) represent reactivated older faults. (2) A regionally persistent northwest-southeast to west-northeast-east-southeast extension direction reactivated northeast- to north-striking structures as predominantly normal dip-slip faults. (3) The half-grabens are lozenge-shaped basins in which subsidence-fault slip was greatest at or near the center of the BFS and decreased to zero toward either end. (4) Transverse folds in the hanging walls immediately adjacent to the BFS formed as a result of higher-frequency variations in subsidence. (5) Subsidence also decreased in a direction perpendicular to the BFS. (6) Intrabasinal faults are overwhelmingly synthetic and predominantly post-depositional. (7) Younger strata progressively onlap prerift rocks of the hanging wall block; this indicates that the basins grew both in width and length as they filled. (8) In all basins initial sedimentation was fluvial, reflecting an oversupply of sediment with respect to basin capacity. (9) Sediments were derived largely from the hanging wall block, which sloped toward the basin, and from streams that entered the basin axially; a direct footwall source was minor, owing to footwall uplift. (10) In strike-slip-dominated basins, subsidence was considerably less than in dip-slip basins, and mosaics of strike- and dip-slip faults are common.

Schlische, R.W. (Rutgers Univ., New Brunswick, NJ (United States)); Olsen, P.E. (Columbia Univ., Palisades, NY (United States))

1991-03-01

74

Oil source rocks in lacustrine sequences from Tertiary grabens, western Mediterranean rift system, northeast Spain  

SciTech Connect

Lacustrine sequences, 100-250 m thick, containing oil-prone, organic-rich mudstones (ORM) are exposed in five Tertiary basins in northeastern Spain. They were deposited in small lacustrine basins (up to 50 km/sup 2/) that developed in grabens of the western Mediterranean rift system. ORMs from the Rubielos basin comprise laminated gray mudstones with interbedded rhythmite intervals (up to 2.5 m thick) formed by couplets of organic- and carbonate-rich laminae (< 1 mm thick). In marginal zones, ORMs (up to 10 m thick) alternate with lean, bioturbated green marls (up to 5 m thick). ORMs (Rock-Eval yields /approximately/ 40 kg/MT, HI /approximately/ 850 mg HC/g TOC) had a dominant waxy terrestrial plant input, with significant and variable algal/bacterial input. ORMs in these basins are immature for petroleum generation. Larger lacustrine basins similar to those described above, in more appropriate burial/thermal situations, can be envisioned as zones of potential interest for lacustrine oil exploration in the western Mediterranean.

Anadon, P.; Cawley, S.J.; Julia, R.

1988-08-01

75

Analogy between natural gas found in lakes of rift valley system of east Africa and its allied gas in Japan  

SciTech Connect

The Afar triangle in northeastern Ethiopia is where the Red Sea rift, the Carlsberg Ridge of the Indian Ocean, and the Rift Valley system of east Africa meet. In 1979, J. Welhan and H. Craig reported that hydrothermal vents at 21/sup 0/N, on the East Pacific Rise, are discharging turbid waters. Mixtures of the plumes with ambient seawater contain significant amounts of dissolved H/sub 2/ and CH/sub 4/ as well as mantel-derived /sup 3/He-rich helium. The /sup 3/He//sup 4/He ratios of rock samples obtained earlier by J. Lupton and H. Craig from the Mid-Oceanic Ridge, including the Mid-Atlantic Ridge and the east Pacific Rise, are extremely high at an almost constant value of (1.3 +/- 0.2) x 10/sup -5/, which they defined as the MOR-type helium. However, the deep brines of the Red Sea contain about 1,000 times more methane than normal seawater does, according to Gold and Soter in 1980. Much evidence leads us to believe that large amounts of /sup 3/He-rich helium-bearing natural gas have been gushing out in many places of the Rift Valley of east Africa for a long time. In 1980, Gold and Soter stated that Lake Kivu, which occupies part of the East African rift valley, contains 50 million tons of dissolved methane for which there is no adequate microbial source. The Japanese Islands began to separate from the Asian continent during the early Miocene. The early Miocene was characterized by intensive volcanic activity that produced large amounts of pyroclastics and other volcanic rocks, generally called green tuff in Japan. It has been suggested that oil and gas in green tuff is derived from the upper mantle.

Fukuta, O.

1984-09-01

76

Fluvial systems response to rift margin tectonics: Makhtesh Ramon area, southern Israel  

NASA Astrophysics Data System (ADS)

The geomorphic evolution of Makhtesh Ramon, a feather-shaped erosional valley, and the Nahal Neqarot drainage system to the south occurred largely in response to tectonic activity along the Dead Sea Rift and its western shoulder. Remnants of Miocene clastic sediments (Hazeva Formation) deposited on an erosional peneplain that formed over this area during the Oligocene epoch provide a datum plane for reconstructing subsequent fluvial evolution. These clastic remnants are presently located on the shoulders of Makhtesh Ramon at various elevations. The peneplain truncating the Makhtesh Ramon block has been tilted 0.7% northeastward since the Pliocene epoch (post-Hazeva Formation), whereas that of the Neqarot syncline, south of the Ramon, has been tilted 1.2%. The elliptical exposure of friable Lower Cretaceous sandstone, exposed in the core of the truncated Ramon structure, governed the development of a new ENE directed (riftward) drainage system through capture of streams that previously drained toward the Mediterranean Sea to the northwest. Incised fluvial gaps in the southern rim of Makhtesh Ramon and alluvial fan relicts within Makhtesh Ramon attest to original drainage into the Makhtesh from the south. Remnants of the Plio-Pleistocene Arava Conglomerate on the eastern end of the Neqarot syncline contain clasts from rocks exposed within Makhtesh Ramon, also indicating that streams flowed into the Makhtesh from the southern Neqarot block through the western gaps, then turning eastward and exiting the Makhtesh via the next (Sha'ar-Ramon) gap to the east. Further down-faulting of the Neqarot block during Mid-Late Pleistocene time led to westward retreat of the Neqarot valley and capture of the last stream flowing northward into the Ramon, leaving the modern Makhtesh Ramon isolated from the southern drainage system.

Ben-David, Ram; Eyal, Yehuda; Zilberman, Ezra; Bowman, Dan

2002-06-01

77

Cenozoic rift formation in the northern Caribbean  

NASA Astrophysics Data System (ADS)

Rifts 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 rifts 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 rifts become progressively younger westward; (2) a two-phase subsidence history in a rift exposed by upthrusting in Jamaica; (3) the absence of rifts east of Jamaica; and (4) the observation that removal of 1400 km of strike-slip displacement on the Cayman Trough fault system places the Paleogene rifts of Jamaica in an active area of extension south of Yucatan where the rifts of Honduras and Guatemala are forming today.

Mann, P.; Burke, K.

1984-12-01

78

Continental rift evolution: From rift initiation to incipient break-up in the Main Ethiopian Rift, East Africa  

NASA Astrophysics Data System (ADS)

The Main Ethiopian Rift is a key sector of the East African Rift System that connects the Afar depression, at Red Sea-Gulf of Aden junction, with the Turkana depression and Kenya Rift to the South. It is a magmatic rift that records all the different stages of rift evolution from rift initiation to break-up and incipient oceanic spreading: it is thus an ideal place to analyse the evolution of continental extension, the rupture of lithospheric plates and the dynamics by which distributed continental deformation is progressively focused at oceanic spreading centres. The first tectono-magmatic event related to the Tertiary rifting was the eruption of voluminous flood basalts that apparently occurred in a rather short time interval at around 30 Ma; strong plateau uplift, which resulted in the development of the Ethiopian and Somalian plateaus now surrounding the rift valley, has been suggested to have initiated contemporaneously or shortly after the extensive flood-basalt volcanism, although its exact timing remains controversial. Voluminous volcanism and uplift started prior to the main rifting phases, suggesting a mantle plume influence on the Tertiary deformation in East Africa. Different plume hypothesis have been suggested, with recent models indicating the existence of deep superplume originating at the core-mantle boundary beneath southern Africa, rising in a north-northeastward direction toward eastern Africa, and feeding multiple plume stems in the upper mantle. However, the existence of this whole-mantle feature and its possible connection with Tertiary rifting are highly debated. The main rifting phases started diachronously along the MER in the Mio-Pliocene; rift propagation was not a smooth process but rather a process with punctuated episodes of extension and relative quiescence. Rift location was most probably controlled by the reactivation of a lithospheric-scale pre-Cambrian weakness; the orientation of this weakness (roughly NE-SW) and the Late Pliocene (post 3.2 Ma)-recent extensional stress field generated by relative motion between Nubia and Somalia plates (roughly ESE-WNW) suggest that oblique rifting conditions have controlled rift evolution. However, it is still unclear if these kinematical boundary conditions have remained steady since the initial stages of rifting or the kinematics has changed during the Late Pliocene or at the Pliocene-Pleistocene boundary. Analysis of geological-geophysical data suggests that continental rifting in the MER evolved in two different phases. An early (Mio-Pliocene) continental rifting stage was characterised by displacement along large boundary faults, subsidence of rift depression with local development of deep (up to 5 km) asymmetric basins and diffuse magmatic activity. In this initial phase, magmatism encompassed the whole rift, with volcanic activity affecting the rift depression, the major boundary faults and limited portions of the rift shoulders (off-axis volcanism). Progressive extension led to the second (Pleistocene) rifting stage, characterised by a riftward narrowing of the volcano-tectonic activity. In this phase, the main boundary faults were deactivated and extensional deformation was accommodated by dense swarms of faults (Wonji segments) in the thinned rift depression. The progressive thinning of the continental lithosphere under constant, prolonged oblique rifting conditions controlled this migration of deformation, possibly in tandem with the weakening related to magmatic processes and/or a change in rift kinematics. Owing to the oblique rifting conditions, the fault swarms obliquely cut the rift floor and were characterised by a typical right-stepping arrangement. Ascending magmas were focused by the Wonji segments, with eruption of magmas at surface preferentially occurring along the oblique faults. As soon as the volcano-tectonic activity was localised within Wonji segments, a strong feedback between deformation and magmatism developed: the thinned lithosphere was strongly modified by the extensive magma intrusion and extension was facilitated

Corti, Giacomo

2009-09-01

79

Age of Fault Movements in Tanzanian Sector of East African Rift System  

Microsoft Academic Search

THE Neogene volcanic province of northern Tanzania is a southerly extension of the more extensive volcanic areas of Ethiopia and Kenya. It stands astride the Eastern Rift Valley and represents a complex interplay of volcanic activity and widespread Earth movements with associated faulting. A general picture is that an older series of basaltic-trachytic shield volcanoes, together with smaller nephelinitic centres,

R. M. MacIntyre

1974-01-01

80

Continental Rifts  

NASA Astrophysics Data System (ADS)

Continental Rifts, edited by A. M. Quennell, is a new member of the Benchmark Papers in Geology Series, edited in toto by R. W. Fairbridge. In this series the individual volume editors peruse the literature on a given topic, select a few dozen papers of ostensibly benchmark quality, and then reorder them in some sensible fashion. Some of the original papers are republished intact, but many are chopped into “McNuggets™” of information. Depending upon the volume editor, the chopping process can range from a butchering job to careful and prudent pruning. The collecting, sifting, and reorganizing tasks are, of course, equally editor-sensitive. The end product of this series is something akin to a set of Reader's Digest of Geology.

Rosendahl, B. R.

81

From hyper-extended rifts to orogens: the example of the Mauléon rift basin in the Western Pyrenees (SW France)  

NASA Astrophysics Data System (ADS)

An integral part of plate tectonic theory is that the fate of rifted margins is to be accreted into mountain belts. Thus, rift-related inheritance is an essential parameter controlling the evolution and architecture of collisional orogens. Although this link is well accepted, rift 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 rift structures. In this orogen the Late Cretaceous and Tertiary convergence overprints a Late Jurassic to Lower Cretaceous complex intracontinental rift system related to the opening of the North Atlantic. During the rifting, 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 rifting 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 rift architecture of the Mauléon basin. Two major diachronous detachment systems 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 final 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-extended rift system. In our presentation, we discuss the compressional reactivation of the rift structures by the study of dip sections across the basin, from weakly reactivated sections in the west to strongly reactivated sections in the east. Comparing the sections, it results that the compression reactivated the rift structures (mainly the detachment faults) and that this reactivation occurred in 2 steps. It corresponds to the reactivation through time of the NMB before the SMB. This evolution is in line with an early proto-subduction of the hyper-extended domain beneath the European plate whereas the NMB sediments are wedged, folded and thrust onto the Iberia and Europe margins ("thin-skin" tectonics). The second step occurs when the deformation started to migrate southward resulting in the formation of the axial Pyrenees nappe stack (thick-skin tectonics). These results suggest that the inherited rift structures strongly controlled the initial convergence. Future work will revisit the more reactivated Albian basins throughout the chain to investigate how far the results from western Pyrenees can be used to understand the Central and Eastern Pyrenees. Moreover, this field-oriented study can serve as an example of how rift structures may control style and timing of orogenic processes.

Masini, E.; Manatschal, G.; Tugend, J.

2011-12-01

82

Middle Proterozoic to Cambrian Rifting, Central North America  

Microsoft Academic Search

The 1100 Ma Midcontinent Rift System in central North America, with its exposed Keweenawan volcanic and plutonic rocks in the Lake Superior region, is one of the major rift-related magmatic provinces in the world. Recent geophysical, petrologic, and geologic studies of the rift and related rocks have made the system one of the best studied structures of this type.Middle Proterozoic

W. Randall Van Schmus

1998-01-01

83

Lithospheric structure of the Rio Grande rift.  

PubMed

A high-resolution, regional passive seismic experiment in the Rio Grande rift region of the southwestern United States has produced new images of upper-mantle velocity structure and crust-mantle topography. Synthesizing these results with geochemical and other geophysical evidence reveals highly symmetric lower-crustal and upper-mantle lithosphere extensional deformation, suggesting a pure-shear rifting mechanism for the Rio Grande rift. Extension in the lower crust is distributed over a region four times the width of the rift's surface expression. Here we propose that the laterally distributed, pure shear extension is a combined effect of low strain rate and a regionally elevated geotherm, possibly abetted by pre-existing lithospheric structures, at the time of rift initiation. Distributed extension in the lower crust and mantle has induced less concentrated vertical mantle upwelling and less vigorous small-scale convection than would have arisen from more localized deformation. This lack of highly focused mantle upwelling may explain a deficit of rift-related volcanics in the Rio Grande rift compared to other major rift systems such as the Kenya rift. PMID:15729338

Wilson, David; Aster, Richard; West, Michael; Ni, James; Grand, Steve; Gao, Wei; Baldridge, W Scott; Semken, Steve; Patel, Paresh

2005-02-24

84

Stratigraphic Record of the Early Mesozoic Breakup of Pangea in the Laurasia-Gondwana Rift System  

NASA Astrophysics Data System (ADS)

Rift basins of the Central Atlantic Margins (CAM) of North America and Morocco preserve largely continental sequences of sedimentary strata and less important minor basalt flows spanning much of the early Mesozoic. The best known is the Newark basin of New Jersey, New York, and Pennsylvania where an astronomically calibrated magnetic polarity time scale is developed. Lacustrine cycles of Milankovitch origin are commonly present in CAM basins, with the period changing from 10 ky (paleoequator with coals), to 20 ky (4 deg--10 deg N), to perhaps 40 ky northward with evaporites. Cycles of {approximately}100 ky, 413 ky, and {approximately}2 my are also important. Four mostly unconformity-bounded tectonostratigraphic sequences are present. The Anisian TS I is fluvial and eolian. TS II--TS IV (Late Triassic to Early Jurassic), consist of "tripartite" lacustrine sequences caused by extension pulses. The Newark basin accumulation rate history allows comparison with quantitative rift basin models. The North American plate's slow northward drift resulted in a relative shift of climate, although the rapid humidification during the latest Triassic and Early Jurassic is associated with a sea-level rise. The Triassic-Jurassic mass extinction is of independent origin, plausibly impact related.

Olsen, Paul E.

85

Continental rifting parallel to ancient collisional belts: an effect of the mechanical anisotropy of the lithospheric mantle  

Microsoft Academic Search

Analysis of major rift systems suggests that the preexisting structure of the lithosphere is a key parameter in the rifting process. Rift propagation is not random, but tends to follow the trend of the orogenic fabric of the plates, systematically reactivating ancient lithospheric structures. Continental rifts often display a clear component of strike–slip deformation, in particular in the early rifting

Andréa Tommasi; Alain Vauchez

2001-01-01

86

Effect of Depleted Continental Lithosphere Counter-flow and Inherited Crustal Weakness on Rifting of the Newfoundland-Iberia and Nova Scotia-Morocco Continental Margins  

NASA Astrophysics Data System (ADS)

In the past two decades, significant advances have been made in understanding the present-day structure of rifted continental margins using reflection and refraction seismic techniques. Despite these advances, we have only a rudimentary understanding of the processes involved in the development of non-volcanic rifted margins, particularly the role of depth-dependant crustal extension, inherited crustal weaknesses, flow of lower continental mantle lithosphere, and syn-rift sedimentation. In this study we use 2D thermo-mechanical finite element modeling to investigate the evolution of upper-mantle scale systems (1200 km wide, 600 km deep). The results are compared with the Newfoundland - Iberia and Nova Scotia - Morocco conjugate margin pairs. The models include thick (200 km) chemically depleted mantle lithosphere, inherited crustal weaknesses, and syn-rift sedimentation. Depending on the properties of the crust and mantle, two types of two-layer two-stage rift systems develop: Type I margins where the crust remains coupled to the mantle lithosphere during rifting producing narrow margins in which the crust necks before the mantle lithosphere; Type II margins where the crust is weaker allowing it to decouple from the mantle during extension producing wide margins in which the mantle necks before the crust finally rifts. When the lithosphere is thick and chemically depleted (e.g., cratonic as an end-member), the hotter buoyant lower mantle lithosphere flows toward to rift axis during rifting allowing the formation of exhumed continental mantle lithosphere. The result is the formation of wide tracts of exhumed mantle lithosphere, subsequently serpentinized owing to hydration, which forms transitional crust between extended continental crust and oceanic crust, consistent with observations of serpentinized continent-derived mantle rocks in the transitional crust region of the Newfoundland - Iberia conjugates, and similar interpretations from the northern Nova Scotia margin. When offset weak zones are included in the crust, these zones become the focus of early extension, but later become abandoned as rifting progressively shifts to the central rift axis. The degree to which the offset weak zones accommodate extension is dependant on the position of the weak zones, the strength of the crust, and syn-rift sedimentation. When the crust is relatively strong, the offset weak zones evolve into narrow (<50 km) syn-rift sedimentary basins. When the crust is relatively weak, or if syn-rift sedimentation is more pronounced, the offset basins remain active longer, and evolve into significantly wider basins. Model results will illustrate how offset weak zones and thick depleted mantle lithosphere flow can result in complex multi-stage rifting that has implications for the timing and structural evolution of syn-rift sediment depocenters.

Ings, S. J.; Beaumont, C.

2011-12-01

87

The distribution of basaltic volcanism on Tenerife, Canary Islands: Implications on the origin and dynamics of the rift systems  

Microsoft Academic Search

One of the most characteristic features of volcanic islands is the existence of rift zones defined commonly as orientated eruptive fissures or parallel rows of elongate cinder cones and dyke swarms. Occasionally, these rifts can appear at the birth of the volcanic island and persist until the last episodes of its constructions, controlling the form and structure of the island

A. Geyer; J. Martí

2010-01-01

88

Magma genesis by rifting of oceanic lithosphere above anomalous mantle: Terceira Rift, Azores  

Microsoft Academic Search

The Terceira Rift formed relatively recently (~1 Ma ago) by rifting of the old oceanic lithosphere of the Azores Plateau and is currently spreading at a rate of 2-4mm\\/a. Together with the Mid-Atlantic Ridge, the Terceira Rift forms a triple junction that separates the Eurasian, African, and American Plates. Four volcanic systems (São Miguel, João de Castro, Terceira, Graciosa), three

Christoph Beier; Karsten M. Haase; Wafa Abouchami; Marc-S. Krienitz; Folkmar Hauff

2008-01-01

89

Magma genesis by rifting of oceanic lithosphere above anomalous mantle: Terceira Rift, Azores  

Microsoft Academic Search

The Terceira Rift formed relatively recently (?1 Ma ago) by rifting of the old oceanic lithosphere of the Azores Plateau and is currently spreading at a rate of 2–4mm\\/a. Together with the Mid-Atlantic Ridge, the Terceira Rift forms a triple junction that separates the Eurasian, African, and American Plates. Four volcanic systems (São Miguel, João de Castro, Terceira, Graciosa), three

Christoph Beier; Karsten M. Haase; Wafa Abouchami; Marc-S. Krienitz; Folkmar Hauff

2008-01-01

90

Mercury isotopic composition of hydrothermal systems in the Yellowstone Plateau volcanic field and Guaymas Basin sea-floor rift  

USGS Publications Warehouse

To characterize mercury (Hg) isotopes and isotopic fractionation in hydrothermal systems 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 rift. These samples provide an initial indication of the variability in Hg isotopic composition among marine and continental hydrothermal systems that are controlled predominantly by mantle-derived magmas. Fluid samples from Ojo Caliente hot spring in Yellowstone range in ?202Hg from - 1.02‰ to 0.58‰ (± 0.11‰, 2SD) and solid precipitate samples from Guaymas Basin range in ?202Hg from - 0.37‰ to - 0.01‰ (± 0.14‰, 2SD). Fluid samples from Ojo Caliente display mass-dependent fractionation (MDF) of Hg from the vent (?202Hg = 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 ?202Hg value to the atmosphere. A small amount of mass-independent fractionation (MIF) was observed in all samples from Ojo Caliente (?199Hg = 0.13‰ ±1 0.06‰, 2SD) but no significant MIF was measured in the sea-floor rift 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.

Sherman, L. S.; Blum, J. D.; Nordstrom, D. K.; McCleskey, R. B.; Barkay, T.; Vetriani, C.

2009-01-01

91

Geophysical diagnosis of Mid-Continent rift  

SciTech Connect

Of all recognized rift systems, the Mid-Continent rift may be the most geophysically analyzed of its genre. The data base associated with this 1900-km (1180-mi) long plate tectonic feature is evenly distributed between gravity, magnetics, and seismology. Since 1983, the western arm of the rift, traced from northeastern Kansas into the Lake Superior basin, has become an oil and gas exploration frontier. The target source and reservoir rocks are of Proterozoic Y (middle Keweenawan) age (1047 +/- 35 Ma minimum). Associated sedimentary and igneous rocks crop out only in northwestern Wisconsin and the adjacent upper peninsula of Michigan. Workers have developed various geophysical models for the Mid-Continent rift, and with the advent of economic interest, the classical compressive, central horst model has been questioned. Geophysical diagnosis of the Mid-Continent rift has gone through three stages. In stage I (late 1930s to 1978), the rift was discovered and identified, and its basic outline, geographic extent, and preliminary structural model were developed. In stage II (1978-1981), the Consortium for Continental Reflection Profiling conducted surveys in Kansas and Michigan, which suggested the rift was an extensional, subsiding trough. Now, in stage III (1984 to present), reflection seismology studies along the entire western area of the rift permit a new review. Examples of industrially acquired lines will be presented.

Dickas, A.B.

1986-05-01

92

The 1.1-Ga Midcontinent Rift System, central North America: sedimentology of two deep boreholes, Lake Superior region  

NASA Astrophysics Data System (ADS)

The Midcontinent Rift System (MRS) of central North America is a 1.1-Ga, 2500-km long structural feature that has been interpreted as a triple-junction rift 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 distributed over a 1300-km distance along the better known southwest arm of the triple-junction MRS, and can be correlated rather well with the units that are exposed in the Lake Superior region. However, a definitive explanation of the anomalous, deeper St. Amour stratigraphy is elusive and any explanation is tenuous. A possible explanation for this anomalous stratigraphy may be the geographic proximity of the St. Amour borehole to the Keweenawan Hot Spot (mantle plume), the suggested thermal force behind the development of the MRS. Similarly, a drastic change in structural architecture may be explained by this geographic relationship. Thus, within the locale of this rifting center, complexities of expansion tectonics may well be responsible for igneous and sedimentary sequences that differ considerably from those found farther west along the rift arm.

Ojakangas, Richard W.; Dickas, Alert B.

2002-03-01

93

Calibration Systems Final Report  

SciTech Connect

The Calibration Systems project at Pacific Northwest National Laboratory (PNNL) is aimed towards developing and demonstrating compact Quantum Cascade (QC) laser-based calibration systems for infrared imaging systems. These on-board systems 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 systems. 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.

Myers, Tanya L.; Broocks, Bryan T.; Phillips, Mark C.

2006-02-01

94

Granular mechanics and rifting  

NASA Astrophysics Data System (ADS)

Numerical models have proved useful in the interpretation of seismic-scale images of rifted margins. In an effort to both test and further illuminate predictions of numerical models, workers have made some strides using map-scale field relations, microstructures, and strain analyses. Yet, fundamental predictions of modeling and tectonic restorations are not able to capture critical observations. For example, many models and interpretations call on continuous faults with restorable kinematic histories. In contrast, s-reflectors and other interpreted shear fabrics in the middle crust tend to be discontinuous and non-planar across a margin. Additionally, most rift-evolution models and interpretations call on end-member ductile flow laws over a range of mechanical and thermal conditions. In contrast, field observations have found that a range of "brittle" fault rocks (e.g., cataclasites and breccias) form in the deeper crust. Similarly, upper crustal materials in deep basins and fault zones can deform through both distributed and localized deformation. Altogether, there appears to be reason to bring a new perspective to aspects of the structural evolution of rifted margins. A granular mechanics approach to crustal deformation studies has several important strengths. Granular materials efficiently localize shear and exhibit a range of stick-slip behaviors, including quasi-viscous rheological responses. These behaviors emerge in discrete element models, analog-materials experiments, and natural and engineered systems regardless of the specific micromechanical flow law. Yet, strictly speaking, granular deformation occurs via failure of frictional contacts between elastic grains. Here, we explore how to relate granular-mechanics models to mesoscale (outcrop) structural evolution, in turn providing insight into basin- and margin- scale evolution. At this stage we are focusing on analog-materials experiments and micro-to-mesoscale observations linking theoretical predictions to structural geological observations. With this combined approach we seek to establish characteristic length scales such as grain sizes and shear zone thicknesses, and time-scales such as stick-slip event dynamics. This would allow us to define a flow law at the mesoscale from comparing the experimental results and the field observations. This rheology could eventually be used to model the strain localization history of rifted margins

Reber, Jacqueline E.; Hayman, Nicholas W.; Lavier, Luc L.

2013-04-01

95

Evolution of Rifting in Africa  

Microsoft Academic Search

Studies of seismicity, age of faulting, age of volcanoes and short and long wavelength gravity anomalies all indicate that the evolution of the East African rift system is related to attenuation and early stages of break-up of the African plate.

R. W. Girdler; J. D. Fairhead; R. C. Searle; W. T. C. Sowerbutts

1969-01-01

96

A Rift Valley fever risk surveillance system for Africa using remotely sensed data: potential for use on other continents.  

PubMed

The authors developed a monitoring and risk mapping system using normalized difference vegetation index (NDVI) times series data derived from the advanced very high resolution radiometer (AVHRR) instrument on polar orbiting national oceanographic and atmospheric administration (NOAA) satellites to map areas with a potential for a Rift Valley fever (RVF) outbreaks in sub-Saharan Africa. This system is potentially an important tool for local, national and international organisations involved in the prevention and control of animal and human disease, permitting focused and timely implementation of disease control strategies several months before an outbreak. We are currently developing a geographic information system (GIS)-based remotely sensed early warning system for potential RVF vectors in the United States. Forecasts of the potential emergence of mosquito vectors will be disseminated throughout the United States, providing several months' warning in advance of potentially elevated mosquito populations. This would allow timely, targeted implementation of mosquito control, animal quarantine and vaccine strategies to reduce or prevent animal and human disease. PMID:20422546

Linthicum, Kenneth J; Anyamba, Assaf; Britch, Seth C; Chretien, Jean-Paul; Erickson, Ralph L; Small, Jennifer; Tucker, Compton J; Bennett, Kristine E; Mayer, Richard T; Schmidtmann, Edward T; Andreadis, Theodore G; Anderson, John F; Wilson, William C; Freier, Jerome E; James, Angela M; Miller, Ryan S; Drolet, Barbara S; Miller, Scott N; Tedrow, Christy A; Bailey, Charles L; Strickman, Daniel A; Barnard, Donald R; Clark, Gary G; Zou, Li

97

Tectonics of the Baikal Rift Deduced from Volcanism and Sedimentation: A Review Oriented to the Baikal and Hovsgol Lake Systems  

Microsoft Academic Search

As known from inland sedimentary records, boreholes, and geophysical data, the initiation of the Baikal rift basins began\\u000a as early as the Eocene. Dating of volcanic rocks on the rift shoulders indicates that volcanism started later, in the Early\\u000a Miocene or probably in the Late Oligocene. Prominent tectonic uplift took place at about 20 Ma, but information (from both\\u000a sediments

Alexei V. Ivanov; Elena I. Demonterova

98

New Geophysical Results About the Relationship Between the Reelfoot Rift and the Rifted Margin of Laurentia  

Microsoft Academic Search

The Reelfoot rift beneath the northern Mississippi embayment is an intracratonic graben system, which formed Early Cambrian time as a result of continental breakup, and has been subsequently reactivated by compressional or tensional stresses related to plate tectonic interactions. It strikes northeastward into the continent, and is approximately perpendicular to the rifted margin of the Laurentia that is shaped by

L. Guo; G. R. Keller

2010-01-01

99

Off-axis volcanism in the Gregory rift, east Africa: implications for models of continental rifting  

SciTech Connect

The largest volcanic centers of the Gregory rift occur in two belts located 100 to 150 km east and west of the axis of the rift 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 systems with the base of a regionally thinned lithosphere. These detachment systems 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 rift axis, indicating that the polarity of the underlying active detachment systems also reverses. The detachments are separated laterally by regional oblique-slip accommodation zones typified by wrench-style tectonism. Off-axis from the rift, 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 rift 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 rift 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 rift may be applicable to Phanerozoic continental rifts in general.

Bosworth, W.

1987-05-01

100

Mesozoic fault reactivation along the St. Lawrence Rift System as constrained by (U-Th/He) thermochronology  

NASA Astrophysics Data System (ADS)

The Saint Lawrence Rift System (SLRS) is a half-graben, extending for 1000 km along St. Lawrence River valley. Late Proterozoic-Early Paleozoic faults of the graben form the contact with the metamorphic Grenvillian basement to the northwest and extend under the Paleozoic sedimentary sequences of the St. Lawrence Lowlands to the southeast. The SLRS is the second most seismically active area in Canada, but the causes of this activity remain unclear. Reactivation of the SLRS is believed to have occurred along Late Proterozoic to Early Paleozoic normal faults related to the opening of the Iapetus Ocean. The absence of strata younger than the Ordovician makes difficult to determine when the faults reactivated after the Ordovician. Field relations between the normal faults bordering the SLRS and those produced by the Charlevoix impact crater suggest a reactivation of the rift younger than the Devonian, the estimated age of the impact. Apatite (U-Th)/He thermochronology is an adequate tool to recognize thermal events related to fault movements. A thermochronology study was then started along three transects across the SLRS, from Québec up to Charlevoix. Apatites were extracted and separated from five granitic to charnockitic gneisses and an amphibolite of Grenvillian age. The samples were exposed on hanging wall and footwall of the Montmorency and Saint-Laurent faults at three different locations along the SLRS. For precision and accuracy, each of the six samples was analyzed for radiogenic 4He and U-Th contents at least twice. Apatite grains were isolated by heavy liquids and magnetic separation. For each sample, ten apatite grains were selected under optical microscope and inserted into Pt capsules. Particular care was taken to isolate apatite free of mineral and fluid inclusions. Indeed, SEM investigations showed that some inclusions are U-rich monazite, which is a supplementary source of 4He to be avoided. The 4He content was determined by using a static noble gas mass spectrometer in CRPG-Nancy and duplicates using a quadrupole mass spectrometer at GEOTOP-UQAM. 4He was measured against internal He gas standards and Durango apatite, with the reference U-Th/He age of 31.13 ± 1.01 Ma. U and Th contents were determined at CRPG-Nancy and duplicated at McGill University by ICP-MS. Preliminary results of U-Th/He on St.-Laurent fault yield an age of 137±12 Ma for the hanging wall, at Sault-au-Cochon and 118±10 Ma for a sample from the footwall, at Cap-aux-oies. Previous Apatite Fission Track (AFT) performed for the two locations gave expected older ages at 149±16 Ma and 196±19 Ma for the hanging wall and the footwall, respectively. These preliminary U-Th/He results are consistent with AFT ages of the area (i.e. as expected, U-Th/He ages are younger than AFT ages) but do not yet provide new constraints for the structural evolution of the St. Lawrence rift system. We are determining further U-Th/He ages and these ages will constrain an exhumation model of the region.

Bouvier, L.; Pinti, D. L.; Tremblay, A.; Minarik, W. G.; Roden-Tice, M. K.; Pik, R.

2011-12-01

101

The case for nearly continuous extension of the West Antarctic Rift System, 105-25 Ma (Invited)  

NASA Astrophysics Data System (ADS)

It is a common perception that extension in the West Antarctic Rift System (WARS) was a two-phase process, with a Cretaceous phase ending when the Campbell Plateau rifted 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.

Wilson, D. S.; Luyendyk, B. P.

2010-12-01

102

Time and length scales of continental rifting: New perspectives for studies of rifting and rupture processes (Invited)  

NASA Astrophysics Data System (ADS)

Studies of active and ancient continental rift systems worldwide show consistent temporal and spatial patterns that are independent of geodynamic setting, as well as pre-existing crustal and lithospheric heterogeneities. These patterns indicate that the thermal and mechanical properties of the lithosphere are fundamentally important during rift initiation. The linkage of propagating, growing fault systems with maximum length proportional to plate strength leads to a regular basin segmentation pattern that is largely independent of pre-rift basement fabric. The mechanical stretching occurs with or without magma intrusion, which also introduces its own scaling and temporal factors. As stretching leads to more thinning, advective and conductive heat transfer from magmatic intrusions locally reduces the plate strength, and magma intrudes to shallower levels. Stresses will also localize along these hot, weak intrusion zones, maintaining the spatial location of magmatism during progressive rifting episodes, and potentially determining the location of plate rupture. Combined satellite geodesy and seismic studies provide new perspectives on the time scales of rifting processes, and motivate reconsideration of time-averaged strain patterns. Observations at continental and oceanic rifts show that tensile stresses from far-field plate motions accumulate over decades before being released during relatively short-lived rifting events. Strain release during magmatic rifting events can be largely aseismic. As Earthscope moves across the Mid-Continent rift to the rifted East Coast passive margin, the breadth and depth of new data sets provides many opportunities to address fundamental questions of continental rifting and rupture: What are the mechanisms and feedbacks controlling along-axis segmentation from rift initiation to breakup, and what are the timescales and rates of processes? How do these differ in magma-rich and magma-poor rift sectors? These questions can be addressed through comparisons between active and ancient rifts, and between magma-rich and magma-poor sectors.

Ebinger, C. J.

2009-12-01

103

Continental rifting on Earth and Mars - A comparison  

NASA Astrophysics Data System (ADS)

The formation of continental rift systems on Earth is connected to prerift uplift generated by upwelling mantle plumes and extensional stresses which originate from remote plate boundary forces. Continental rifting and continental breakup on Earth are therefore intimately connected to Earth's plate tectonic environment. Recently, Martian candidate analogues to terrestrial continental rifts have been investigated in detail and it has been shown that the Tempe Fossae, Acheron Fossae and Thaumasia Highland Rifts bear many structural similarities to continental rifts on Earth. However, the question of the rift formation process has so far not been addressed and an active mechanism involving mantle plumes and local doming has usually been assumed. Rifts are also sometimes thought to be at least indirect evidence for plate tectonics, although the connection of Martian rifts to plate tectonic forces has so far not been discussed. We have investigated whether forces connected to plate movement are necessary to initiate rifting and show that lithosphere scale faulting at the Thaumasia Highland Rift is feasible even in the absence of mantle plumes or tensional plate-boundary forces. Rather, stresses originating from horizontal differences of the gravitational potential energy will be shown to be almost sufficient to induce rifting, supporting the hypothesis of a passive rifting mechanism in the Thaumasia Highlands. The emplacement of magma bodies in the upper crust could then sufficiently weaken the lithosphere to initiate lithosphere scale faulting and thus induce rifting. This hypothesis is in good agreement with the observation of rift-related volcanism as well as the fact that faults seem to initiate at volcanoes and propagate away from them before interconnecting. We conclude that rifting on Mars is feasible even if key factors connected to continental rifting on Earth, i.e. plate boundary forces and convection induced drag on the lower lithosphere, are absent. The absence of forces connected to plate tectonics is also consistent with the observed moderate extension of only a few kilometers. These values are typical for young terrestrial rifts (e.g., the Kenya-rift) and failed arms and suggest that large scale plate movement and subduction did not play a role in Martian rifting.

Grott, M.; Hauber, E.; Kronberg, P.

2007-08-01

104

Evaluation of geothermal potential of Rio Grande rift and Basin and Range province, New Mexico. Final technical report, January 1, 1977May 31, 1978  

Microsoft Academic Search

A study was made of the geological, geochemical and geophysical characteristics of potential geothermal areas in the Rio Grande rift 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;

Callender

1985-01-01

105

Trench-parallel flow in the southern Ryukyu subduction system: Effects of progressive rifting of the overriding plate  

NASA Astrophysics Data System (ADS)

AbstractThe Okinawa trough in the Ryukyu subduction <span class="hlt">system</span> is one of a few actively extending back arc basins within the continental lithosphere. Recent shear-wave splitting measurements show variable fast directions along the trough suggesting a complex three-dimensional mantle flow field. In this study we use numerical subduction models to demonstrate that the thickness variations of the continental lithosphere bounding the edge of a subduction zone can result in complicated mantle circulation and regional dynamics. The model results for the southern Ryukyu show a combination of two effects: Along the Okinawa trough, the increasing thickness of the overriding Eurasian plate toward Taiwan due to a gradually diminishing <span class="hlt">rifting</span> induces pressure gradients that drive trench-parallel flow to the edge in the shallow portion of the mantle wedge, and the thick Eurasian lithosphere to the west effectively blocks and diverts this along-arc flow and limits the toroidal flow around the slab edge below it. The toroidal flow thus enters the mantle wedge at depths of more than about 100 km, opposite in direction with and largely below the along-arc flow. These combined geometry effects of the Eurasian lithosphere create an intricate three-dimensional flow structure at the southern edge of the Ryukyu subduction zone. Model predictions for lattice preferred orientations of olivine aggregates show rotation patterns that agree with the observed shear-wave splitting patterns. This three-dimensional scenario echoes the geochemical and seismological evidence worldwide that indicates complex, depth-varying mantle circulations in subduction <span class="hlt">systems</span>.</p> <div class="credits"> <p class="dwt_author">Lin, Shu-Chuan; Kuo, Ban-Yuan</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">106</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011AGUFM.T23A2368L"> <span id="translatedtitle"><span class="hlt">Rifting</span> to spreading in the Gulf of Aden</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Gulf of Aden margins <span class="hlt">systems</span> are volcanic to the West, where they are influenced by the Afar hotspot, and non-volcanic East of longitude 46°E. The combined use of magnetics, gravity, seismic reflection, field observations (tectonic and sedimentological) allowed us to obtain better constraints on the timing of continental <span class="hlt">rifting</span> and seafloor spreading. From the Permo-Triassic to the Oligocene, the Arabian-African plate was subject to distributed extension, probably due, at least from the Cretaceous, to tensile stresses related to the subduction of the Tethysian slab in the north. In Late Eocene, 35 Ma ago, <span class="hlt">rifting</span> started to localize along the future area of continental breakup. Initially guided by the inherited basins, continental <span class="hlt">rifting</span> then occurred synchronously over the entire gulf before becoming localized on the northern and southern borders of the inherited grabens, in the direction of the Afar hot-spot. In the areas with non-volcanic margins (in the East), the faults marking the end of <span class="hlt">rifting</span> trend parallel to the inherited grabens. Only the transfer faults cross-cut the inherited grabens, and some of these faults later developed into transform faults. The most important of these transform faults follow a Precambrian trend. Volcanic margins were formed in the West of the Gulf, up to the Guban graben in the south-east and as far as the southern boundary of the Bahlaf graben in the North-East. Seaward dipping reflectors (SDRs) can be observed on many oil-industry seismic profiles. The influence of the hotspot during <span class="hlt">rifting</span> was concentrated on the western part of the gulf. Therefore, it seems that the western domain was uplifted and eroded at the onset of <span class="hlt">rifting</span>, while the eastern domain was characterized by more continuous sedimentation. The phase of distributed deformation was followed by a phase of strain localization during the <span class="hlt">final</span> <span class="hlt">rifting</span> stage, just before formation of the Ocean-Continent Transition (OCT), in the most distal graben (DIM graben). About 20 Ma ago, the emplacement of the OCT started in the east with exhumation of the subcontinental mantle. Farther west, the <span class="hlt">system</span> was heated up by the strong influence of the Afar hot-spot, which led to breakup with much less extension. In the Gulf of Aden (s.str), up to the Shukra El Sheik fracture zone, oceanic spreading started 17.6 Ma ago. West of this fracture zone, oceanic accretion started 10 Ma ago, and 2 Ma ago in the Gulf of Tadjoura. Post-<span class="hlt">rift</span> deformation of the eastern margins of the Gulf of Aden can be seen in the distal and proximal domains. Indeed, the substantial post-<span class="hlt">rift</span> uplift of these margins could be associated with either the continental break-up, or activity of the Afar hotspot and related volcanic/magmatic activity. The Afar plume is therefore important for several reasons. It allows the localization of deformation along the Red Sea/Aden <span class="hlt">system</span> and the rapid opening of the Gulf after the continental break-up.</p> <div class="credits"> <p class="dwt_author">Leroy, S.; Razin, P.; Lucazeau, F.; D'Acremont, E.; Autin, J.; Watremez, L.; Robinet, J.; Baurion, C.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">107</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012EGUGA..14.8332H"> <span id="translatedtitle">Kinematics of the South Atlantic <span class="hlt">rift</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Extensional deformation along the South Atlantic, Central African and West Africa <span class="hlt">rift</span> <span class="hlt">systems</span> heralded in the breakup of the western half of the Gondwana supercontinent. The interplay between a complex series of intraplate <span class="hlt">rifts</span> profoundly affected the spatio-temporal localisation of extensional deformation and the resulting geometries of the conjugate South Atlantic margins. We present a new plate kinematic model which quantitatively integrates lithosphere deformation and observations from both passive margins and intracontinental <span class="hlt">rifts</span> in Africa and South America. Our model eliminates the need for previously inferred large offset continental shear zones in southern South America such as the Gastre Fault <span class="hlt">system</span> while satisfying most observations of the onset of subsidence, deformation and <span class="hlt">rifting</span> along the conjugate <span class="hlt">rifted</span> margins and related marginal sedimentary basins. The model indicates that extension became focussed in the South Atlantic <span class="hlt">rift</span> basin by the Earliest Cretaceous, continuing at low extensional velocities, predominantly controlled by African intraplate deformation while there was no deformation along the future Equatorial Atlantic. The Patagonian part of South America acted as an independent plate between Antarctica, Africa, and South America during the Latest Jurassic to Aptian times, hereby opening <span class="hlt">rift</span> basins striking at high angles to the present-day South American margin. By about 125 Ma (Barremian/Aptian) deformation and subsequent weakening along the Equatorial Atlantic <span class="hlt">rift</span> branch yielded a large increase in extensional velocities and a change in extension direction between South America and Africa, while lithospheric extension had progressed far enough to create the enigmatic sub-salt basins in the central South Atlantic. The change in spreading direction largely eliminated intraplate deformation in Patagonia and subsequently resulted in the onset of post-<span class="hlt">rift</span> thermal subsidence in the southern South American basins. Rupture of extended continental lithosphere in the central South Atlantic followed a few million years after this major change in kinematics and is likely responsible for the observed first-order present day margin geometry. We compare our model-derived kinematics against predictions from forward numerical models of lithosphere extension along the conjugate West-African/Brazil and the Equatorial Atlantic margins. We conclude that the multi-velocity, multi-directional <span class="hlt">rift</span> history can consistently explain the first order margin geometry observed in the South Atlantic. We further couple our plate kinematic model with predictive forward mantle flow models that integrate lithospheric deformation to test the influence of mantle-driven topography on the evolving <span class="hlt">rift</span>.</p> <div class="credits"> <p class="dwt_author">Heine, C.; Brune, S.; Young, A.; Zoethout, J.; Flament, N.; Müller, R. D.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-04-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">108</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/6747539"> <span id="translatedtitle">Volcanism at <span class="hlt">rifts</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">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> <div class="credits"> <p class="dwt_author">White, R.S.; McKenzie, D.P.</p> <p class="dwt_publisher"></p> <p class="publishDate">1989-07-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">109</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.dstu.univ-montp2.fr/PERSO/tommasi/tommasi_vauchez_2001.pdf"> <span id="translatedtitle">Continental <span class="hlt">rifting</span> parallel to ancient collisional belts: an e¡ect of the mechanical anisotropy of the lithospheric mantle</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Analysis of major <span class="hlt">rift</span> <span class="hlt">systems</span> suggests that the preexisting structure of the lithosphere is a key parameter in the <span class="hlt">rifting</span> process. <span class="hlt">Rift</span> propagation is not random, but tends to follow the trend of the orogenic fabric of the plates, systematically reactivating ancient lithospheric structures. Continental <span class="hlt">rifts</span> often display a clear component of strike^ slip deformation, in particular in the early</p> <div class="credits"> <p class="dwt_author">Andrea Tommasi; Alain Vauchez</p> <p class="dwt_publisher"></p> <p class="publishDate">2001-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">110</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/1999PEPI..111..253S"> <span id="translatedtitle">Seismicity of oceanic and continental <span class="hlt">rifts</span>—a geodynamic approach</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Two major kinds of divergent structures—oceanic and intracontinental <span class="hlt">rifts</span>—were compared in principal seismic and tectonic characteristics. First, the role of main components of the mid-oceanic ridges (MOR) was estimated for the whole Earth. We considered two levels of the MOR segmentation. The first-order structures are the segments of MOR between triple junctions and the second-order structures are a transform faults and <span class="hlt">rift</span> parts of MOR. The seismic catalogues NEIC and CMT were used to assess the seismic moment release. The seismic moment release was calculated another way using the global plate tectonic model NUVEL-1 and Brune's formulae. Comparison of these two values shows that the seismic coupling coefficient, ?, varies from 1 to 10% for most of MOR and is always higher for transform faults. Most of the deformation, therefore, is aseismic slip. Most seismicity of MOR is confined to transform faults. The energy contribution of transform faults is one to two orders magnitude higher than that of the <span class="hlt">rift</span>, and increases with the spreading rate. There is a strong correlation between the seismic moment release of strike-slip faults and their total lengths. The correlation shows that the seismic moment release depends on the total transform area and confirms the simple thermal model of transform seismicity that was given by Burr and Solomon. The seismic moment release and the spreading rate have opposite patterns. For the <span class="hlt">rifts</span>, there is an inverse correlation between the seismic moment of normal faults and spreading velocity, while it seems for transforms that these parameters are independent. <span class="hlt">Finally</span>, these results show that the seismicity of transforms and <span class="hlt">rifts</span> depends first of all on the thermal structure of oceanic lithosphere. In the case of continental <span class="hlt">rifts</span>, one can distinguish in the degree of seismic activity depending on the stage of <span class="hlt">rifting</span>. Hence, analysis of the continental seismicity requires the consideration of factors of a geological evolution that play practically no role in the case of oceanic lithosphere. The comparison of geological and seismic data for the East African region has allowed us to outline the regular changes of the seismic regime during development of the <span class="hlt">rift</span> zone from the stage of incipient <span class="hlt">rift</span> to mature oceanic <span class="hlt">rift</span>. In the evolutionary series [intracontinental incipient <span class="hlt">rift</span>]-[intracontinental mature <span class="hlt">rift</span>]-[intercontinental <span class="hlt">rift</span>]-[oceanic slow-spreading <span class="hlt">rift</span>]-[oceanic fast-spreading <span class="hlt">rift</span>], there is a gradual decrease of the role of <span class="hlt">rifts</span> (sensu stricto, as tension structures) and increase of the role of strike-slip faults. Epicenters concentrate along major faults as well. The level of seismic energy becomes lower, although the rate of deformation increases.</p> <div class="credits"> <p class="dwt_author">Sobolev, P. O.; Rundquist, D. V.</p> <p class="dwt_publisher"></p> <p class="publishDate">1999-03-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">111</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2003EAEJA....10300H"> <span id="translatedtitle">The Thaumasia "<span class="hlt">rift</span>", Mars - is it a <span class="hlt">rift</span>?</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">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 (?), the tilt of the graben floor (?), and the vertical offset (d). We measure a scarp height d of ˜2000 m and floor tilts ? between 0.9^o and 2.7^o. For ? = 60^o, we obtain values of D between ˜33 km and ˜67 km (? = 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 calculated by other authors from scarp widths and shadows. While the structural geometry of the TR is more similar to classical <span class="hlt">rifts</span> than that of Valles Marineris, there are better Martian analogues to terrestrial continental <span class="hlt">rifts</span>, e.g., Tempe Fossae. Essential characteristics of continental <span class="hlt">rifts</span> are: Regional domal uplift, crustal break-up, formation of through-going <span class="hlt">rift</span> valleys, and <span class="hlt">rift</span>-related volcanism. The structure and morpho-tectonics of the TR and the lack of extension-volcanism do not meet these criteria of terrestrial continental <span class="hlt">rifts</span>. So far, the geodynamic processes that led to the formation of the TR are unclear (crustal break-down due to Thaumasia uplift? magma deficit near Syria Planum? a long-lived and late center of magmatectonic activity?).</p> <div class="credits"> <p class="dwt_author">Hauber, E.; Kronberg, P.</p> <p class="dwt_publisher"></p> <p class="publishDate">2003-04-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">112</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011Tecto..30.1002D"> <span id="translatedtitle">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> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">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> <div class="credits"> <p class="dwt_author">Daoud, Mohamed A.; Le Gall, Bernard; Maury, René C.; Rolet, JoëL.; Huchon, Philippe; Guillou, Hervé</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-02-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">113</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/10158587"> <span id="translatedtitle">Organic Geochemical and tectonic evolution of the Midcontinent <span class="hlt">Rift</span> <span class="hlt">system</span>. <span class="hlt">Final</span> report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The older assemblages stand in contrast with the ca. 1000 Ma old Hunting Formation, Arctic Canada, which contains what may be the oldest evidence for modem algae - red algal fossils that compare closely with members of the extant family Bangiophyceae (Butterfield et al., 1990). Taken together the Nonesuch, Shaler, Hunting and other assemblages support the hypothesis of a major episode of eukaryotic diversification ca. 1000 Ma ago. Prior to this time, eukaryotic primary producers must have been physiologically primitive (and now extinct) algae whose abundance in ecosystems is poorly constrained by analogies with the present oceans. Cyanobacteria were major primary producers in a wide range of marine environments. After 1000 Ma, diversifying red green and chromophyte algae contributed significantly to primary production in all save microbial mat communities in restricted environments. It bears mention that such mat communities remained significant potential sources of buried organic matter until the end of the Proterozoic, necessitating exploration strategies that differ from those commonly employed for younger rocks (Knoll, in press). As in Phanerozoic basins, petroleum exploration in Proterozoic rocks requires tools for stratigraphic correlation. In Neoproterozoic (<1000 Ma) rocks, biostratigraphy is possible, and it is aided significantly by C and Sr isotopic chemostratigraphy. New data from the Shaler Group contribute to the construction of C and Sr isotopic curves for Neoproterozoic time, making possible much improved chronostratigraphy for this time interval. (Asmerom et al., 1991; Hayes et al., ms. in preparation).</p> <div class="credits"> <p class="dwt_author">Hayes, J.M.; Pratt, L.M. [Indiana Univ., Bloomington, IN (United States); Knoll, A.H. [Harvard Univ., Cambridge, MA (United States). Dept. of Organismal and Evolutionary Biology</p> <p class="dwt_publisher"></p> <p class="publishDate">1992-12-31</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">114</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010CoMP..tmp..127S"> <span id="translatedtitle">Geochemistry and geochronology of the mafic lavas from the southeastern Ethiopian <span class="hlt">rift</span> (the East African <span class="hlt">Rift</span> <span class="hlt">System</span>): assessment of models on magma sources, plume-lithosphere interaction and plume evolution</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Major and trace element and isotopic ratios (Sr, Nd and Pb) are presented for mafic lavas (MgO > 4 wt%) from the southwestern Yabello region (southern Ethiopia) in the vicinity of the East African <span class="hlt">Rift</span> <span class="hlt">System</span> (EARS). New K/Ar dating results confirm three magmatic periods of activity in the region: (1) Miocene (12.3-10.5 Ma) alkali basalts and hawaiites, (2) Pliocene (4.7-3.6 Ma) tholeiitic basalts, and (3) Recent (1.9-0.3 Ma) basanite-dominant alkaline lavas. Trace element and isotopic characteristics of the Miocene and Quaternary lavas bear a close similarity to ocean island basalts that derived from HIMU-type sublithospheric source. The Pliocene basalts have higher Ba/Nb, La/Nb, Zr/Nb and 87Sr/86Sr (0.70395-0.70417) and less radiogenic Pb isotopic ratios (206Pb/204Pb = 18.12-18.27) relative to the Miocene and Quaternary lavas, indicative of significant contribution from enriched subcontinental lithospheric mantle in their sources. Intermittent upwelling of hot mantle plume in at least two cycles can explain the magmatic evolution in the southern Ethiopian region. Although plumes have been originated from a common and deeper superplume extending from the core-mantle boundary, the diversity of plume components during the Miocene and Quaternary reflects heterogeneity of secondary plumes at shallower levels connected to the African superplume, which have evolved to more homogeneous source.</p> <div class="credits"> <p class="dwt_author">Shinjo, Ryuichi; Chekol, Takele; Meshesha, Daniel; Itaya, Tetsumaru; Tatsumi, Yoshiyuki</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-11-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">115</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011CoMP..162..209S"> <span id="translatedtitle">Geochemistry and geochronology of the mafic lavas from the southeastern Ethiopian <span class="hlt">rift</span> (the East African <span class="hlt">Rift</span> <span class="hlt">System</span>): assessment of models on magma sources, plume-lithosphere interaction and plume evolution</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Major and trace element and isotopic ratios (Sr, Nd and Pb) are presented for mafic lavas (MgO > 4 wt%) from the southwestern Yabello region (southern Ethiopia) in the vicinity of the East African <span class="hlt">Rift</span> <span class="hlt">System</span> (EARS). New K/Ar dating results confirm three magmatic periods of activity in the region: (1) Miocene (12.3-10.5 Ma) alkali basalts and hawaiites, (2) Pliocene (4.7-3.6 Ma) tholeiitic basalts, and (3) Recent (1.9-0.3 Ma) basanite-dominant alkaline lavas. Trace element and isotopic characteristics of the Miocene and Quaternary lavas bear a close similarity to ocean island basalts that derived from HIMU-type sublithospheric source. The Pliocene basalts have higher Ba/Nb, La/Nb, Zr/Nb and 87Sr/86Sr (0.70395-0.70417) and less radiogenic Pb isotopic ratios (206Pb/204Pb = 18.12-18.27) relative to the Miocene and Quaternary lavas, indicative of significant contribution from enriched subcontinental lithospheric mantle in their sources. Intermittent upwelling of hot mantle plume in at least two cycles can explain the magmatic evolution in the southern Ethiopian region. Although plumes have been originated from a common and deeper superplume extending from the core-mantle boundary, the diversity of plume components during the Miocene and Quaternary reflects heterogeneity of secondary plumes at shallower levels connected to the African superplume, which have evolved to more homogeneous source.</p> <div class="credits"> <p class="dwt_author">Shinjo, Ryuichi; Chekol, Takele; Meshesha, Daniel; Itaya, Tetsumaru; Tatsumi, Yoshiyuki</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-07-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">116</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010AGUFM.T33D2293G"> <span id="translatedtitle">New Geophysical Results About the Relationship Between the Reelfoot <span class="hlt">Rift</span> and the <span class="hlt">Rifted</span> Margin of Laurentia</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Reelfoot <span class="hlt">rift</span> beneath the northern Mississippi embayment is an intracratonic graben <span class="hlt">system</span>, which formed Early Cambrian time as a result of continental breakup, and has been subsequently reactivated by compressional or tensional stresses related to plate tectonic interactions. It strikes northeastward into the continent, and is approximately perpendicular to the <span class="hlt">rifted</span> margin of the Laurentia that is shaped by the southeast-striking Alabama-Oklahoma transform fault. The northern section of the <span class="hlt">rift</span> near the town of New Madrid, Missouri, was the site of three great 1811-1812 earthquakes, and it remains the most seismically active area east of the Rocky Mountains. However, the southern end of the <span class="hlt">rift</span> is obscure, and the relationship between the Reelfoot <span class="hlt">rift</span> and the <span class="hlt">rifted</span> margin of Laurentia remains disputed. We analyzed the gravity and magnetic database for the region using new data enhancement techniques to shed some light on this relationship. We analyzed a large area to assess the regional geological structure. Complete Bouguer gravity data and and total magnetic intensity (TMI) data were assembled and gridded on a regular grid with spacing of 2km, the TMI data were then reduced to the magnetic pole. Then the data were processed with standard techniques to attenuate the high-frequency noise, and we analyzed the regional and residual anomalies. Specially, we calculated the tilt-angle derivatives of the data. We then calculated the directional horizontal derivatives of the tilt-angle derivatives both along and perpendicular to the strike of the <span class="hlt">rift</span>. The maps of these derivatives clearly delineate the boundaries of the edges of the Reelfoot <span class="hlt">rift</span>, the leading edge of the Ouachita thrust belt and the margin of Laurentia. The results of the preliminary processing indicate that the southern end of the <span class="hlt">rift</span> is near the leading edge of the Ouachita thrust belt, which produces a more curvilinear shape for the Laurentian margin than the very linear Alabama-Oklahoma transform fault suggesting its structure is more complex than usually depicted.</p> <div class="credits"> <p class="dwt_author">Guo, L.; Keller, G. R.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">117</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012Litho.152...84W"> <span id="translatedtitle">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> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">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 by reverse zoning in alkali feldspar and linear compatible trace element patterns.</p> <div class="credits"> <p class="dwt_author">White, John Charles; Espejel-García, Vanessa V.; Anthony, Elizabeth Y.; Omenda, Peter</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-11-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">118</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012EGUGA..1413307P"> <span id="translatedtitle">Continental <span class="hlt">rifting</span> and upper mantle strength</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The uppermost mantle traditionally has been considered to be relatively strong compared to the crust. However, this view has recently been contested based on improved assessments of earthquake focal depths and considerations regarding effective elastic thickness, and caused much subsequent debate. Here we employ a high resolution, numerical model of continental <span class="hlt">rifting</span> calibrated with topographic, gravimetric and seismological observations in order to constrain the strength of the uppermost mantle. Our model shows that a <span class="hlt">rift</span> developing in the presence of a relatively strong uppermost mantle leads to lithospheric necking well beneath the Moho. This is consistent with previous models of lithospheric extension, but here we identify two important inconsistencies with observations from both recent and ancient continental <span class="hlt">rifts</span>: 1): Necking beneath the Moho leads to downwards dislocation of the Moho beneath the <span class="hlt">rift</span>. However, seismological studies always indicate that the Moho tends to shallow beneath <span class="hlt">rifts</span>. 2): Deep necking additionally causes the development of regionally supported and unrealistically high flank uplifts together with associated extreme gravity anomalies. By modelling the thermo mechanical development of continental <span class="hlt">rift</span> flanks at a range of lithosphere thicknesses and mantle strengths and comparing with topographic profiles from a global set of recent <span class="hlt">rift</span> <span class="hlt">systems</span>, we show that the strength of the uppermost mantle should be no more than 200 MPa. Our numerical model employs a self consistent representation of the lithosphere by including equilibrium small-scale convection which contributes with a relatively constant sub-crustal heat flux. Since the lithospheric mantle is colder and thus denser than the asthenosphere below, continental <span class="hlt">rifting</span> requires a certain level of strength of the mantle in order to avoid unstable lithospheric delamination. We find this lower strength limit to be less than 20 MPa. Uppermost mantle strength in the range of 20-200 MPa is typically less than that of the crust and of previous estimates of upper mantle strength. Previous numerical studies require a strong uppermost mantle in order to obtain localized deformation as evident from narrow continental <span class="hlt">rifts</span>. However, our model shows that <span class="hlt">rifts</span> developing in weak mantle lithosphere, relative to the crust, indeed tend to become narrow.</p> <div class="credits"> <p class="dwt_author">Petersen, K. D.; Nielsen, S. B.; Stephenson, R.; Gerya, T.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-04-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">119</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.mna.it/MER/utilities.htm"> <span id="translatedtitle">Evolution of Oblique <span class="hlt">Rifting</span> on the Main Ethiopian <span class="hlt">Rift</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://nsdl.org/nsdl_dds/services/ddsws1-1/service_explorer.jsp">NSDL National Science Digital Library</a></p> <p class="result-summary">Movie showing the evolution of oblique <span class="hlt">rifting</span> in analogue models (from Corti, 2008, Nature Geosc). Obliquity in this model is 30° (angle between the normal to the <span class="hlt">rift</span> axis and the direction of extension). Note the two-phase <span class="hlt">rift</span> evolution with a first phase of boundary fault activity and basin subsidence, followed by activation of en-echelon arranged internal faults obliquely cutting the <span class="hlt">rift</span> floor.</p> <div class="credits"> <p class="dwt_author">Corti, Giacomo</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">120</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010PEPI..181...82K"> <span id="translatedtitle">Shear wave anisotropy of the Godavari <span class="hlt">rift</span> in the south Indian shield: <span class="hlt">Rift</span> signature or APM related strain?</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Shear wave splitting analysis using SKS, SKKS and S waveforms recorded at eight broadband seismic stations within and in the vicinity of the Proterozoic Godavari <span class="hlt">rift</span> <span class="hlt">system</span> in the south Indian shield yielded 104 new measurements of azimuthal anisotropy. Our results reveal that the delay times lie between 0.70 and 1.20 s, similar to the previous measurements from the Indian shield. The orientations of fast polarization directions at most of the stations within and beyond the <span class="hlt">rift</span> are generally aligned orthogonal to the <span class="hlt">rift</span> axis, consistent with asthenospheric flow in the extension direction. Absence of clear evidences for a preferentially thinner lithosphere beneath the Godavari <span class="hlt">rift</span> or anomalously high heat flow values coupled with the fact that the NE oriented fast polarization directions are also close to the APM direction of the Indian plate, result in an ambiguity in interpreting the results as being due to strain related to plate motion or signatures of <span class="hlt">rifting</span>. A thin lithosphere beneath the <span class="hlt">rift</span> suggests that the source of anisotropy is likely to be in the asthenosphere. In such a scenario, either the mechanism of (1) active <span class="hlt">rifting</span> where the asthenospheric flow drives the <span class="hlt">rifting</span> or (2) passive <span class="hlt">rifting</span> where mantle flow responds to lithospheric thinning caused by far field stresses or (3) present day APM related strain appear to be the plausible mechanisms for forging the observed anisotropy.</p> <div class="credits"> <p class="dwt_author">Kumar, Narendra; Kumar, M. Ravi; Singh, Arun; Solomon Raju, P.; Purnachandra Rao, N.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-08-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_5");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a onClick='return showDiv("page_3");' 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title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_6");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a onClick='return showDiv("page_3");' href="#">3</a> <a onClick='return showDiv("page_4");' href="#">4</a> <a onClick='return showDiv("page_5");' href="#">5</a> <a onClick='return showDiv("page_6");' href="#">6</a> <a style="font-weight: bold;">7</a> <a onClick='return showDiv("page_8");' href="#">8</a> <a onClick='return showDiv("page_9");' href="#">9</a> <a onClick='return showDiv("page_10");' href="#">10</a> <a onClick='return showDiv("page_11");' href="#">11</a> <a onClick='return showDiv("page_12");' href="#">12</a> <a onClick='return showDiv("page_13");' href="#">13</a> <a onClick='return showDiv("page_14");' href="#">14</a> <a onClick='return showDiv("page_15");' href="#">15</a> <a onClick='return showDiv("page_16");' href="#">16</a> <a onClick='return showDiv("page_17");' href="#">17</a> <a onClick='return showDiv("page_18");' href="#">18</a> <a onClick='return showDiv("page_19");' href="#">19</a> <a onClick='return showDiv("page_20");' href="#">20</a> <a onClick='return showDiv("page_21");' href="#">21</a> <a onClick='return showDiv("page_22");' href="#">22</a> <a onClick='return showDiv("page_23");' href="#">23</a> <a onClick='return showDiv("page_24");' href="#">24</a> <a onClick='return showDiv("page_25");' href="#">25</a> </span> </span> <a id="NextPageLink" onclick='return showDiv("page_8");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">121</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009GeoJI.179..549B"> <span id="translatedtitle">InSAR observations of 2007 Tanzania <span class="hlt">rifting</span> episode reveal mixed fault and dyke extension in an immature continental <span class="hlt">rift</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">In the early stages of continental <span class="hlt">rifting</span>, extension takes place by normal faulting, while in mature continental <span class="hlt">rifts</span> dyke intrusion dominates. Little is known about the nature of the transition between fault-controlled and dyke-controlled extension or about the processes in an intermediate setting. Here, we present observations of the temporal and spatial evolution of surface displacements during the 2007 July 14-August 4 <span class="hlt">rifting</span> episode in Northern Tanzania, an immature section of the East African <span class="hlt">Rift</span>. The ground deformation initiated with subsidence that can be attributed to ~40 cm of normal motion on a NE striking fault. Following July 17, deformation was dominated by the intrusion of ~7-km-long dyke. Dyke opening increased gradually to a total of ~2.4 m. From July 21, the collapse of a shallow graben above the fault dominated the near-field displacements. Comparison to the 2007 Dabbahu dyke, Afar, which occurred in a more mature <span class="hlt">rift</span>, shows an order-of-magnitude scale difference in dyke length. Using numerical models of dyke propagation, we attribute this to the size and depth of the magma chamber; in immature <span class="hlt">rifts</span> the thick crust and slow spreading rate favour small, deep magma chambers, forming short, buried dykes, whereas in mature <span class="hlt">rifts</span> the thinner crust and faster spreading rate favour large, shallow magma chambers and long, erupting dykes. Observing the pattern of active processes in the East African <span class="hlt">Rift</span> is key to understanding the development of <span class="hlt">rift</span> <span class="hlt">systems</span> and passive margins elsewhere.</p> <div class="credits"> <p class="dwt_author">Biggs, Juliet; Amelung, Falk; Gourmelen, Noel; Dixon, Timothy H.; Kim, Sang-Wan</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-10-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">122</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40564095"> <span id="translatedtitle">Basin neotectonics of Lakes Edward and George, East African <span class="hlt">Rift</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The Edward and George lake basins are located in the western branch of the East African <span class="hlt">Rift</span> <span class="hlt">System</span> (EARS). Both basins occupy half grabens with the main boundary fault located in the west and are separated by a high relief accommodation zone. This structural high formed where the NNE–SSW trend of the Miocene <span class="hlt">rifting</span> and NW–SE oriented basement lineaments interfere.</p> <div class="credits"> <p class="dwt_author">Tine Lærdal; Michael R Talbot</p> <p class="dwt_publisher"></p> <p class="publishDate">2002-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">123</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.agu.org/journals/jb/v076/i008/JB076i008p01967/JB076i008p01967.pdf"> <span id="translatedtitle">Ethiopian <span class="hlt">Rift</span> and Plateaus: Some Volcanic Petrochemical Differences</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Volcanism on the Arabo-Ethiopian swell has accompanied the development of the three traversing spreading zones conjoining at Afar: the Red Sea, Gulf of Aden, and African <span class="hlt">rift</span> <span class="hlt">systems</span>. The Red Sea and Gulf of Aden floors are formed by oceanic tholerites, but Afar and the main Ethiopian <span class="hlt">rift</span> show a wider range of more alkaline volcanics, related to slower crustal</p> <div class="credits"> <p class="dwt_author">P. A. Mohr</p> <p class="dwt_publisher"></p> <p class="publishDate">1971-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">124</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/54162020"> <span id="translatedtitle">Structural evolution of the Abiquiu embayment, Rio Grande <span class="hlt">Rift</span>: Implications for the development of transfer zones</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The Abiquiu embayment is located along the boundary between the Colorado Plateau and the Rio Grande <span class="hlt">rift</span> in north central New Mexico. It is an early <span class="hlt">rift</span> basin bordered by the Canones fault <span class="hlt">system</span> on its west side that is oblique to the regional trend of the Rio Grande <span class="hlt">rift</span> and lies within a region where the polarity of the</p> <div class="credits"> <p class="dwt_author">R. T. Hicks; M. A. Murphy</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">125</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/54498272"> <span id="translatedtitle">Neotectonic Stress Analysis Of The Red Sea <span class="hlt">Rift</span> By Finite Element Modeling</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The Red Sea is a tectonic <span class="hlt">rift</span> that was formed in the late Oligocene-early Miocene when the originally connected African and Arabian land masses broke apart. At first it was a continental <span class="hlt">rift</span>, then, as Arabia drifted away, developed into an intercontinental <span class="hlt">system</span> that today separates the independent Arabian plate from the African plate. The Red Sea <span class="hlt">rift</span> is part</p> <div class="credits"> <p class="dwt_author">S. K. Dwivedi; D. Hayashi</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">126</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009AGUFM.T13A1850C"> <span id="translatedtitle">Post <span class="hlt">Rift</span> Thermal Evolution of Extended Lithosphere</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">An improved thermal model of the lithosphere extension is proposed and its influence in the petroleum <span class="hlt">system</span> in sedimentary basins examined. The new model assumes existence of time dependent variation in the lithosphere thickness during the post-<span class="hlt">rift</span> period, which was not take account in the formulation of the Mackenzie model (1978). In the present work we assume that the asymptotic growth of the lithosphere thickness, during the post-<span class="hlt">rift</span> period, may be represented by an asymptotic relation of the type: L(t)=(L/?)+(L-L/?)erf(?*t) where L(t) is lithospheric thickness at post-<span class="hlt">rift</span> time t, ? the stretching factor as defined in the McKenzie model, erf the error function and ? a suitable scaling constant. According to the above equation the syn-<span class="hlt">rift</span> value of L is (L/?). For large times the thickness of the lithosphere approaches asymptotically the pre-<span class="hlt">rift</span> value of L. The value of ? can be determined by calculating the time necessary for the stretched lithosphere (L/?) to return to original thickness. The results of numerical simulations indicate that the heat flux derived from the new model is substantially lower than the values predicted by the McKenzie model (see Figure 1). The new model has been calibrated using available information on evolution of thermal maturity indices for the Santos Basin, situated in the offshore area of southeast Brazil. Heat flow variations during the post stretch period, for the case in which the stretching factor is 2.5.</p> <div class="credits"> <p class="dwt_author">Cardoso, R. R.; Hamza, V. M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">127</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013EGUGA..15.6616M"> <span id="translatedtitle">Stratigraphic Modelling of Continental <span class="hlt">Rifting</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Interlinks between deformation and sedimentation have long been recognised as an important factor in the evolution of continental <span class="hlt">rifts</span> and basins development. However, determining the relative impact of tectonic and climatic forcing on the dynamics of these <span class="hlt">systems</span> remains a major challenge. This problem in part derives from a lack of modelling tools capable of simulated high detailed surface processes within a large scale (spatially and temporally) tectonic setting. To overcome this issue an innovative framework has been designed using two existing numerical forward modelling codes: Underworld, capable of simulating 3D self-consistent tectonic and thermal lithospheric processes, and Tellus, a forward stratigraphic and geomorphic modelling framework dedicated to simulating highly detailed surface dynamics. The coupling framework enables Tellus to use Underworld outputs as internal and boundary conditions, thereby simulating the stratigraphic and geomorphic evolution of a realistic, active tectonic setting. The resulting models can provide high-resolution data on the stratigraphic record, grain-size variations, sediment provenance, fluvial hydrometric, and landscape evolution. Here we illustrate a one-way coupling method between active tectonics and surface processes in an example of 3D oblique <span class="hlt">rifting</span>. Our coupled model enables us to visualise the distribution of sediment sources and sinks, and their evolution through time. From this we can extract and analyse at each simulation timestep the stratigraphic record anywhere within the model domain. We find that even from a generic oblique <span class="hlt">rift</span> model, complex fluvial-deltaic and basin filling dynamics emerge. By isolating the tectonic activity from landscape dynamics with this one-way coupling, we are able to investigate the influence of changes in climate or geomorphic parameters on the sedimentary and landscape record. These impacts can be quantified in part via model post-processing to derive both instantaneous and cumulative erosion/sedimentation.</p> <div class="credits"> <p class="dwt_author">Mondy, Luke; Duclaux, Guillaume; Salles, Tristan; Thomas, Charmaine; Rey, Patrice</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-04-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">128</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/55021116"> <span id="translatedtitle">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> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">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</p> <div class="credits"> <p class="dwt_author">J. C. Behrendt</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">129</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/55925162"> <span id="translatedtitle">Post <span class="hlt">Rift</span> Thermal Evolution of Extended Lithosphere</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">An improved thermal model of the lithosphere extension is proposed and its influence in the petroleum <span class="hlt">system</span> in sedimentary basins examined. The new model assumes existence of time dependent variation in the lithosphere thickness during the post-<span class="hlt">rift</span> period, which was not take account in the formulation of the Mackenzie model (1978). In the present work we assume that the asymptotic</p> <div class="credits"> <p class="dwt_author">R. R. Cardoso; V. M. Hamza</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">130</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2008AGUFM.T43A1976M"> <span id="translatedtitle">Forensic investigation of <span class="hlt">rift</span>-to-drift transitions and volcanic <span class="hlt">rifted</span> margins birth</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">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> <div class="credits"> <p class="dwt_author">Meyer, R.; Hertogen, J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">131</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/1999GeCoA..63.3653W"> <span id="translatedtitle">An active subcontinental mantle volatile <span class="hlt">system</span> in the western Eger <span class="hlt">rift</span>, Central Europe: Gas flux, isotopic (He, C, and N) and compositional fingerprints</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The composition and flux of gas emanations, and the isotopic ratios of CO 2, He and N 2 of 74 mineral springs and dry gas vents (mofettes) in the western Eger <span class="hlt">rift</span> (Czech Republic) have been analyzed. Four geochemically similar, but tectonically separate, gas escape centers are distinguishable, out of which 3 show a free gas flux >85000 dm 3 h -1. All gases from the centers are CO 2-rich (>99 vol.%) and have ? 13C values ranging from -1.8 to -4.0‰. 3He/ 4He ratios are as high as R/R a = 5, and are among the highest measured in Europe. The discharge of the gas mixture decreases with distance from the emanation centers with both decreasing fractions of CO 2 and ? 13C values, whereas the fractions of N 2 and trace gases increase. These changes in chemical and isotopic composition are associated by a decrease in R/R a ratios from about 5 in the centers to <2 in the peripheries. The changes of the contents and isotopic composition of CO 2 can be explained by physico-chemical fractionations of CO 2 between gaseous and aqueous phases. Towards the periphery, the contents of free CO 2 and its ? 13C are reduced by dissolution of CO 2 in groundwater, whereby the content of N 2 increases. 3He/ 4He ratios give evidence for mixing of He from both a deep-seated magmatic and a crustal source. The gas emanation centers, with their strongly magmatic ? 13C value of about -2.7‰, seem to outline the intersections of the Eger <span class="hlt">rift</span> and the Mariánské Lázn? fault, which are considered to represent a deep-reaching fracture <span class="hlt">system</span> that enables the ascent of gases from a magmatic body in the European subcontinental mantle (SCM). Therefore, the European SCM is suspected to be the main source of CO 2. The most mantle-like He (and probably N 2) occurs in the centers of gas release. The total regional gas flux in the western Eger <span class="hlt">rift</span> is determined to be 3.6 × 10 8 mol a -1. When related to the investigated area of 1500 km 2, flux densities greater than 0.24 × 10 6, 52, and 0.65 mol km -2 a -1 for CO 2, N 2 and He respectively are calculated.</p> <div class="credits"> <p class="dwt_author">Weinlich, F. H.; Bräuer, K.; Kämpf, H.; Strauch, G.; Tesa?, J.; Weise, S. M.</p> <p class="dwt_publisher"></p> <p class="publishDate">1999-11-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">132</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/5788199"> <span id="translatedtitle">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> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">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> <div class="credits"> <p class="dwt_author">Callender, J.F.</p> <p class="dwt_publisher"></p> <p class="publishDate">1985-04-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">133</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.oie.int/boutique/extrait/613-624gerdes.pdf?PHPSESSID=a43083ef616217ee1fa2c72fe2d5ae24"> <span id="translatedtitle"><span class="hlt">Rift</span> Valley fever</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Summary <span class="hlt">Rift</span> Valley fever (RVF) is an arthropod-borne viral disease of ruminants, camels and humans. It is also a significant zoonosis which may be encountered as an uncomplicated influenza-like illness, but may also present as a haemorrhagic disease with liver involvement; there may also be ocular or neurological lesions. In animals, RVF may be inapparent in non-pregnant adults, but outbreaks</p> <div class="credits"> <p class="dwt_author">G. H. Gerdes</p> <p class="dwt_publisher"></p> <p class="publishDate">2004-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">134</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009AGUFM.T23F..06D"> <span id="translatedtitle">Amagmatic Accretionary Segments, Ultraslow Spreading and Non-Volcanic <span class="hlt">Rifted</span> Margins (Invited)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">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 simultaneously on both the Newfoundland and Iberian Margins in the Jurassic and Cretaceous. Miocene Lena Trough is a new mid-ocean <span class="hlt">rift</span> plate boundary and the <span class="hlt">final</span> event in the separation of the North American and Eurasian continents. Mapping and sampling of Lena Trough confirms that it is both oblique and amagmatic, showing that initiation of seafloor spreading at a non-volcanic <span class="hlt">rifted</span> continental margin follows the same pattern as ultraslow spreading ridges.</p> <div class="credits"> <p class="dwt_author">Dick, H. J.; Snow, J. E.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">135</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2005AGUSM.T43B..07A"> <span id="translatedtitle">Structural Evolution of the Incipient Okavango <span class="hlt">Rift</span> Zone, NW Botswana</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">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 strongly influenced by the position of these pre-existing faults. Evidence of fault linkage is seen along some of the faults. Linked segments of faults are well defined and some are > 200 km long. We suggest from this result that fault linkage and propagation occurred very early and prior to significant basin development. We conclude that basement fabric seems to be a controlling factor at least in the early stages of basin architecture and structural evolution of ORZ.</p> <div class="credits"> <p class="dwt_author">Atekwana, E. A.; Kinabo, B. D.; Modisi, M. P.; Hogan, J. P.; Wheaton, D. D.</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-05-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">136</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/55876636"> <span id="translatedtitle">Tectonic Inheritance, Continental <span class="hlt">Rifts</span> and the Transition to Segmented Seafloor Spreading: Results From Analogue and Numerical Models</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">We use analogue and numerical models to investigate the role of an inherited structural grain on continental <span class="hlt">rifting</span> and the implications for oceanic ridge segmentation after continental breakup. Our models are based on geological observations from the western branch of the East African <span class="hlt">Rift</span> <span class="hlt">System</span>. The basins of this <span class="hlt">rift</span> <span class="hlt">system</span> are located within Proterozoic mobile belts at the edge</p> <div class="credits"> <p class="dwt_author">G. Corti; J. W. van Wijk</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">137</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013Tectp.583...88L"> <span id="translatedtitle">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> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">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> <div class="credits"> <p class="dwt_author">Loule, Jean-Pierre; Pospisil, Lubomil</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">138</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011CoMP..162..651W"> <span id="translatedtitle">Magma mixing in the 1100 AD Montaña Reventada composite lava flow, Tenerife, Canary Islands: interaction between <span class="hlt">rift</span> zone and central volcano plumbing <span class="hlt">systems</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Zoned eruption deposits commonly show a lower felsic and an upper mafic member, thought to reflect eruption from large, stratified magma chambers. In contrast, the Montaña Reventada composite flow (Tenerife) consists of a lower basanite and a much thicker upper phonolite. A sharp interface separates basanite and phonolite, and chilled margins at this contact indicate the basanite was still hot upon emplacement of the phonolite, i.e. the two magmas erupted in quick succession. Four types of mafic to intermediate inclusions are found in the phonolite. Inclusion textures comprise foamy quenched ones, others with chilled margins and yet others that are physically mingled, reflecting progressive mixing with a decreasing temperature contrast between the end-members. Analysis of basanite, phonolite and inclusions for majors, traces and Sr, Nd and Pb isotopes show the inclusions to be derived from binary mixing of basanite and phonolite end-members in ratios of 2:1 to 4:1. Although, basanite and phonolite magmas were in direct contact, contrasting 206Pb/204Pb ratios show that they are genetically distinct (19.7193(21)-19.7418(31) vs. 19.7671(18)-19.7807(23), respectively). We argue that the Montaña Reventada basanite and phonolite first met just prior to eruption and had limited interaction time only. Montaña Reventada erupted from the transition zone between two plumbing <span class="hlt">systems</span>, the phonolitic Teide-Pico Viejo complex and the basanitic Northwest <span class="hlt">rift</span> zone. A <span class="hlt">rift</span> zone basanite dyke most likely intersected the previously emplaced phonolite magma chamber. This led to eruption of geochemically and texturally unaffected basanite, with the inclusion-rich phonolite subsequently following into the established conduit.</p> <div class="credits"> <p class="dwt_author">Wiesmaier, S.; Deegan, F. M.; Troll, V. R.; Carracedo, J. C.; Chadwick, J. P.; Chew, D. M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-09-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">139</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2004Tectp.394...87T"> <span id="translatedtitle">Processing and interpretation of the gravity field of the East African <span class="hlt">Rift</span>: implication for crustal extension</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Compilation of new and existing gravity data were undertaken to assess the nature of the crust beneath the East African <span class="hlt">Rift</span> <span class="hlt">System</span>. Using 3D gravity modeling code crustal model of gravity profiles across two sectors of the <span class="hlt">rift</span> were computed. The results are discussed in light of the structure of the <span class="hlt">rift</span> <span class="hlt">system</span>. The results of the 3D modeling of gravity profiles across the two <span class="hlt">rift</span> zones revealed northward thinning of the crust. The maximum crustal attenuation occurs beneath the Afar depression, indicating the Afar <span class="hlt">rift</span> undergoes an intense fragmentation of the crust resulting from faulting and magmatic activity. However, our computed crustal thickness below the Afar depression falls within an upper bound compared to elsewhere below tectonically active <span class="hlt">rift</span> zones. This can be explained in terms of crustal accretion resulting from an impact of the Afar mantle plume since ˜30 Ma ago. The residual gravity obtained using high-cut filtering techniques reveals significant density contrast between the northern and southern sectors of the <span class="hlt">rift</span>. The northern part of the <span class="hlt">rift</span> is characterized by regular patterns of positive gravity anomalies, which can be interpreted in terms of a zone of crustal thinning through which relatively dense materials have intruded the overlying crust. In contrast, south of the Main Ethiopian <span class="hlt">Rift</span>, the anomalies are characterized by random patterns and low amplitudes. The along-<span class="hlt">rift</span>-axis variation in gravity anomalies implies that the style of crustal deformation changed progressively, beginning with regionally distributed crustal deformation, such as the one we observe within the more juvenile and wider southern segment of the <span class="hlt">rift</span>, to localized deformation within the active and narrow <span class="hlt">rift</span> zones of the northern sector of the Ethiopian <span class="hlt">Rift</span>. We suggest that the key parameters controlling along-<span class="hlt">rift</span>-axis variation in gravity anomalies are the rate of crustal extension, faulting and magmatic activities.</p> <div class="credits"> <p class="dwt_author">Tessema, A.; Antoine, L. A. G.</p> <p class="dwt_publisher"></p> <p class="publishDate">2004-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">140</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/5580485"> <span id="translatedtitle">Experimental lithium <span class="hlt">system</span>. <span class="hlt">Final</span> report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">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> <div class="credits"> <p class="dwt_author">Kolowith, R.; Berg, J.D.; Miller, W.C.</p> <p class="dwt_publisher"></p> <p class="publishDate">1985-04-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_6");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" 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showDiv("page_24");' href="#">24</a> <a onClick='return showDiv("page_25");' href="#">25</a> </span> </span> <a id="NextPageLink" onclick='return showDiv("page_9");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">141</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2000RvMP...72...95R"> <span id="translatedtitle"><span class="hlt">Final</span>-focus <span class="hlt">systems</span> in linear colliders</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">In colliding-beam facilities, the ``<span class="hlt">final</span>-focus <span class="hlt">system</span>'' must demagnify the beams to attain the very small spot sizes required at the interaction points. The first <span class="hlt">final</span>-focus <span class="hlt">system</span> with local chromatic correction was developed for the Stanford Linear Collider, where very large demagnifications were desired. This same conceptual design has been adopted by all of the future linear collider designs as well as the Superconducting Super Collider, the Stanford and KEK B Factories, and the proposed Muon Collider. In this paper, the overall layout, physics constraints, and optimization techniques relevant to the design of <span class="hlt">final</span>-focus <span class="hlt">systems</span> for high-energy electron-positron linear colliders are reviewed. <span class="hlt">Finally</span>, advanced concepts to avoid some of the limitations of these <span class="hlt">systems</span> are discussed.</p> <div class="credits"> <p class="dwt_author">Raubenheimer, T. O.; Zimmermann, F.</p> <p class="dwt_publisher"></p> <p class="publishDate">2000-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">142</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/5426478"> <span id="translatedtitle">Laboratory test <span class="hlt">system</span>. <span class="hlt">Final</span> report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">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> <div class="credits"> <p class="dwt_author">Asher, G.L.</p> <p class="dwt_publisher"></p> <p class="publishDate">1980-03-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">143</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2006AGUFM.T31B0454T"> <span id="translatedtitle">Baikal <span class="hlt">Rift</span> Zone: Intra-cratonic <span class="hlt">rifting</span> without Moho uplift</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Baikal <span class="hlt">Rift</span> Zone is located in Siberia at the centre of the world's largest continental area. It provies a unique opportunity for studying the processes of ongoing continental <span class="hlt">rifting</span> in an area with thick cratonic crust. The BEST project (Baikal Explosion Seismic Transects) aims at providing seismic velocity models of the crust and uppermost mantle across and along the strike of the Baikal <span class="hlt">Rift</span> Zone. The project comprises two deep seismic profiles at the southern end of Lake Baikal: (1) a 360 km long, NS-trending profile across the <span class="hlt">rift</span> zone from the Mongolian border to Cheremhovo, and (2) a 360 km long EW-trending profile along-strike of the <span class="hlt">rift</span> zone at the northern shore of the lake into the Tunka depression to the Mongolian border. The seismic sources were 13 explosions in boreholes, airgun shots in the lake, and the supervibrator located at Babushkin near the cross point between the two profiles at the shore of the lake. The velocity models show a gently deepening Moho from the Siberian Craton into the Palaeozoic fold belt to the SE of Lake Baikal without any sign of Moho uplift around the more than 10 km thick sedimentary graben structure. Strong seismic reflectivity slightly offset to the NE from the <span class="hlt">rift</span> zone indicates the presence of pronounced magmatic intrusions in the lower crust, despite of the non-volcanic appearance of much of the <span class="hlt">rift</span> zone. These intrusions may have compensated <span class="hlt">rifting</span> associated lower crustal thinning. Further there is no sign of any reduction of the seismic Pn wave velocity around the <span class="hlt">rift</span> zone. These features indicates that the existing models of continental <span class="hlt">rifting</span> may not be adequate for describing the underlying processes in thick, cratonic lithosphere.</p> <div class="credits"> <p class="dwt_author">Thybo, H.; Nielsen, C.; Jensen, M.; Suvorov, V. D.; Perchuc, E.</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">144</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/44259154"> <span id="translatedtitle">Timing of East African <span class="hlt">Rift</span> development in southern Ethiopia: Implication for mantle plume activity and evolution of topography</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Accurate determination of <span class="hlt">rifting</span> chronology and associateduplift is crucial to understanding the evolution of the EastAfrican <span class="hlt">Rift</span> <span class="hlt">System</span> (EARS) and for identifying the significanceof mantle plumes during continental breakup. This investigationof <span class="hlt">rift</span>-related cooling along a major fault scarp in southernEthiopia, using (U-Th)\\/He thermochronometry, shows that riftingstarted not before 20 Ma. Therefore, there is an absence ofsignificant <span class="hlt">rift</span> activity synchronous with</p> <div class="credits"> <p class="dwt_author">Raphaël Pik; Bernard Marty; Jean Carignan; Gezahegn Yirgu; Teklewold Ayalew</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">145</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/7101426"> <span id="translatedtitle">Multiuser test <span class="hlt">system</span>. <span class="hlt">Final</span> report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">A multiterminal, real-time laboratory test <span class="hlt">system</span> was developed to perform automated electrical testing on electronic components while permitting independent software production to be accomplished from other terminals at the same time. This versatility provides test capability for prototype hardware and evaluation of new product designs for several concurrent development efforts.</p> <div class="credits"> <p class="dwt_author">Cogan, D.L.</p> <p class="dwt_publisher"></p> <p class="publishDate">1980-09-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">146</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/687704"> <span id="translatedtitle">Hydrothermal flow <span class="hlt">systems</span> in the Midcontinent <span class="hlt">Rift</span>: Oxygen and hydrogen isotopic studies of the North Shore Volcanic Group and related hypabyssal sills, Minnesota</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary"><span class="hlt">Rift</span>-related lavas of the North Shore Volcanic Group (NSVG) are intruded by plutonic rocks of the Duluth Complex along the unconformity between the NSVG and the underlying Proterozoic metasedimentary rocks (Animikie Group) and Archean volcano-sedimentary and plutonic rocks. Heat associated with the emplacement of the mafic intrusions generated fluid flow in the overlying plateau lavas. {delta}{sup 18}O values for whole rocks from the NSVG and hypabyssal sills range from 5.5 to 17.7{per_thousand} and 5.3 to 11.5{per_thousand}, respectively, and most values are higher than those considered normal for basaltic rocks (5.4 to 6.0{per_thousand}). In general, there is a positive correlation between whole rock {delta}{sup 18}O and water content, which suggests that elevated {delta}{sup 18}O values are related primarily to secondary mineral growth and isotopic exchange during hydrothermal alteration and metamorphism. {delta}{sup 18}O{sub H{sub 2}O} values computed from amygdule-filling minerals such as smectite, chlorite, and epidote found in low- to high-temperature metamorphic zones range from {approximately}{minus}1 to 6{per_thousand} with an average value of {approximately}3{per_thousand}. Smectite in the lower-grade zones gives computed {delta}D{sub H{sub 2}O} values between {minus}26 and {minus}83{per_thousand}, whereas epidote in the higher-grade zones gives {delta}D{sub H{sub 2}O} values of {minus}15 to 6{per_thousand}. Fluid isotopic compositions computed from epidote and smectite values are suggestive of the involvement of at least two fluids during the early stages of amygdule filling. Fluid {delta}D and {delta}{sup 18}O values determined from epidote at the higher metamorphic grades indicate that seawater dominated the deeper portions of the <span class="hlt">system</span> where greenschist facies assemblages and elevated {delta}{sup 18}O values were produced in flow interiors, as well as margins. Smectite isotopic compositions suggest that meteoric water was predominant in the shallower portions of the <span class="hlt">system</span>. The increase in {delta}{sup 18}O values of massive flow interiors with depth is interpreted as a result of rock interaction with a fluid of constant oxygen isotopic composition with increasing temperature. The stable isotopic data are supportive of previous suggestions that seawater was involved in the hydrothermal <span class="hlt">system</span> associated with the Midcontinent <span class="hlt">Rift</span>. Although the origin of the seawater remains problematic, it appears that marine incursions may have occurred during the late stages of Portage Lake volcanism, and periodically thereafter.</p> <div class="credits"> <p class="dwt_author">Park, Y.R.; Ripley, E.M. [Indiana Univ., Bloomington, IN (United States). Dept. of Geological Sciences</p> <p class="dwt_publisher"></p> <p class="publishDate">1999-06-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">147</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://dx.doi.org/10.1029/2008GC002293"> <span id="translatedtitle">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> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p class="result-summary">[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 the primary control on the mode of extension. ?? 2009 by the American Geophysical Union.</p> <div class="credits"> <p class="dwt_author">Keranen, K. M.; Klemperer, S. L.; Julia, J.; Lawrence, J. F.; Nyblade, A. A.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">148</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/41061622"> <span id="translatedtitle">Cretaceous <span class="hlt">rift</span> related magmatism in central-western South America</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The Cretaceous–Paleocene Andean basin <span class="hlt">system</span> of central-western South America, comprises northwestern Argentina and southwestern Bolivia. It is situated between 62°–68°W and 18°–27°S, but extends westward to northern Chile and northward to Bolivia and Peru. These basins have been interpreted as an aborted foreland <span class="hlt">rift</span>. In a general sense, it may be possible to relate this <span class="hlt">rift</span> to the opening of</p> <div class="credits"> <p class="dwt_author">J. G Viramonte; S. M Kay; R Becchio; M Escayola; I Novitski</p> <p class="dwt_publisher"></p> <p class="publishDate">1999-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">149</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010Tecto..29.5010G"> <span id="translatedtitle">Neoproterozoic <span class="hlt">rifting</span> in the southern Georgina Basin, central Australia: Implications for reconstructing Australia in Rodinia</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">A <span class="hlt">system</span> of northwest striking Neoproterozoic <span class="hlt">rift</span> basins underlies Paleozoic strata in the southern Georgina Basin of central Australia. Normal faults bounding these <span class="hlt">rift</span> basins were selectively reactivated during the mid-Paleozoic Alice Springs Orogeny and are now expressed as high-angle reverse faults that invert the preexisting <span class="hlt">rift</span> basins. Exhumed and eroded <span class="hlt">rift</span> basin remnants are present in the hanging wall of the Oomoolmilla, Lucy Creek, Tarlton, and Toomba reverse faults, and <span class="hlt">rift</span> basins may be preserved in the subsurface beneath the Toko Syncline and Burke River Structural Belt. <span class="hlt">Rift</span> basin fill indicates two periods of extension: a major <span class="hlt">rift</span>-forming episode between approximately 700 and 650 Ma (coeval with Sturtian glacial deposits) and a second episode of extension at approximately 600 Ma (coeval with Marinoan glacial deposits). This northwest striking <span class="hlt">rift</span> <span class="hlt">system</span> in central Australia supports results from other regions, indicating that the Neoproterozoic continental margin of Australia consisted of northwest striking <span class="hlt">rift</span> segments offset by northeast striking transform faults. Such a configuration is geometrically incompatible with a Laurentian continental margin consisting of northeast striking <span class="hlt">rift</span> segments and conflicts with reconstructions such as SWEAT and AUSWUS that match Australia with western Laurentia in the Rodinia supercontinent.</p> <div class="credits"> <p class="dwt_author">Greene, David C.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-10-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">150</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ntis.gov/search/product.aspx?ABBR=ADA225496"> <span id="translatedtitle">Studies of Infection and Dissemination of <span class="hlt">Rift</span> Valley Fever Virus in Mosquitoes (<span class="hlt">Final</span> Report 14 May 86-14 May 89, Annual Report 15 May 88-14 May 89).</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ntis.gov/search/index.aspx">National Technical Information Service (NTIS)</a></p> <p class="result-summary">We have been engaged in a multimethod study of <span class="hlt">Rift</span> Valley fever (RVF) virus in mosquitoes. During this year, we have carried out: (1) immunocytochemical and ultrastructural studies of the proventriculus of adult, female Culex pipiens infected with RVF vi...</p> <div class="credits"> <p class="dwt_author">W. S. Romoser</p> <p class="dwt_publisher"></p> <p class="publishDate">1990-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">151</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2002JGRB..107.2332Y"> <span id="translatedtitle">Response of groundwater <span class="hlt">systems</span> in the Dead Sea <span class="hlt">Rift</span> Valley to the Nuweiba earthquake: Changes in head, water chemistry, and near-surface effects</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Nuweiba earthquake (Mw = 7.1) of November 1995 had significant effects on groundwater heads, spring discharge, and chemistry in the Dead Sea <span class="hlt">Rift</span> Valley. Groundwater heads increased by 6 cm near the Dead Sea (local shallow alluvial aquifer) and by 50 cm near the sea of Galilee (regional deep confined aquifer), some 330 and 460 km north of the epicenter, respectively. In the arid central Arava valley, some 210 km north of the epicenter, the discharge of small springs increased significantly. The increase in spring discharge, as recorded in Moa spring, was accompanied by a marked change in its chemistry. However, while the change in discharge followed the earthquake, the chemistry change was found some 16 days before the earthquake. The effect of the earthquake in Moa was enhanced and prolonged because of a breach in the confinement <span class="hlt">system</span> of the shallow artesian aquifer and the formation of new flow paths along faults, cracks, and dikes. Due to the extreme aridity of the region, the sequence above the aquifer is loaded with soluble salts. Dissolution of these salts by the ascending groundwater accounts for the observed increase in salinity and changes in the spring chemistry with time. Initially, the ascending water flushed the newly formed flow paths, gradually leaching the available soluble salts. Later, as discharge shrank, upward flow was maintained within the already flushed <span class="hlt">system</span>, and the water chemistry returned to the original aquifer composition.</p> <div class="credits"> <p class="dwt_author">Yechieli, Yoseph; Bein, Amos</p> <p class="dwt_publisher"></p> <p class="publishDate">2002-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">152</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/41170513"> <span id="translatedtitle">Deposition and alteration of carbonaceous series within a Neotethyan <span class="hlt">rift</span> at the western boundary of the Arabian Plate: The Late Permian Um Irna Formation, NW Jordan, a petroleum <span class="hlt">system</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">During the late Permian (Kungurian to Kazanian) a Neotethyan <span class="hlt">rift</span> basin evolved at the western boundary of the Arabian Plate, in what is called today the Dead Sea Valley of western Jordan. The break-up of Pangaea was accompanied by low-sinuosity sandy braided- to meandering-fluvial drainage <span class="hlt">systems</span> which were fed by the uplift of the Arabian Shield and by poorly aerated</p> <div class="credits"> <p class="dwt_author">H. G. Dill; A. Bechtel; J. Kus; R. Gratzer; A. M. B. Abu Hamad</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">153</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009Tecto..28.4014B"> <span id="translatedtitle">How sediment promotes narrow <span class="hlt">rifting</span>: Application to the Gulf of California</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">If the gravitational stress changes related to crustal thinning are large enough to affect the mode of extension, then sedimentation should also affect that mode. We propose that the weight of sediments reduces the difference in crustal buoyancy forces caused by local crustal thinning, allowing a <span class="hlt">rift</span> to extend more easily in a narrow <span class="hlt">rift</span> mode. We examine the effect of deposition of large amounts of nonlocally derived sediment on extensional style using two-dimensional, regional-scale numerical experiments of extending thick continental crust with varied initial thermal conditions, geometries, rheological parameters, and sedimentation properties. Depending on initial model conditions, the onset of <span class="hlt">rifting</span> in thick continental crust occurs in the narrow <span class="hlt">rifting</span>, wide <span class="hlt">rifting</span>, or core complex mode. With continued extension, all cases eventually transition to a narrow <span class="hlt">rifting</span> mode. For a <span class="hlt">system</span> in wide <span class="hlt">rift</span> mode, moderate to fast sedimentation shortens the time needed to transition to a narrow <span class="hlt">rift</span>. In the Gulf of California, changes in extensional style correlate with sediment thickness, with an earlier transition to narrow <span class="hlt">rifting</span> in the north versus the south. We compare our model results to the extensional history of the Gulf of California, where sediments may have caused the northern and north central domain of the gulf (Delfin-Tiburon and Guaymas segments) to transition to narrow <span class="hlt">rifting</span> before the south central domains (Alarcon segment).</p> <div class="credits"> <p class="dwt_author">Bialas, Robert W.; Buck, W. Roger</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-08-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">154</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2008GGG.....912013B"> <span id="translatedtitle">Magma genesis by <span class="hlt">rifting</span> of oceanic lithosphere above anomalous mantle: Terceira <span class="hlt">Rift</span>, Azores</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Terceira <span class="hlt">Rift</span> formed relatively recently (˜1 Ma ago) by <span class="hlt">rifting</span> of the old oceanic lithosphere of the Azores Plateau and is currently spreading at a rate of 2-4mm/a. Together with the Mid-Atlantic Ridge, the Terceira <span class="hlt">Rift</span> forms a triple junction that separates the Eurasian, African, and American Plates. Four volcanic <span class="hlt">systems</span> (São Miguel, João de Castro, Terceira, Graciosa), three of which are islands, are distinguished along the axis and are separated by deep avolcanic basins similar to other ultraslow spreading centers. The major element, trace element and Sr-Nd-Pb isotope geochemistry of submarine and subaerial lavas display large along-axis variations. Major and trace element modeling suggests melting in the garnet stability field at smaller degrees of partial melting at the easternmost volcanic <span class="hlt">system</span> (São Miguel) compared to the central and western volcanoes, which appear to be characterized by slightly higher melting degrees in the spinel/garnet transition zone. The degrees of partial melting at the Terceira <span class="hlt">Rift</span> are slightly lower than at other ultraslow mid-ocean ridge spreading axes (Southwest Indian Ridge, Gakkel Ridge) and occur at greater depths as a result of the melting anomaly beneath the Azores. The combined interaction of a high obliquity, very slow spreading rates, and a thick preexisting lithosphere along the axis probably prevents the formation and eruption of larger amounts of melt along the Terceira <span class="hlt">Rift</span>. However, the presence of ocean islands requires a relatively stable melting anomaly over relatively long periods of time. The trace element and Sr-Nd-Pb isotopes display individual binary mixing arrays for each volcanic <span class="hlt">system</span> and thus provide additional evidence for focused magmatism with no (or very limited) melt or source interaction between the volcanic <span class="hlt">systems</span>. The westernmost mantle sources beneath Graciosa and the most radiogenic lavas from the neighboring Mid-Atlantic Ridge suggest a mantle flow from Graciosa toward the Mid-Atlantic Ridge and hence a flux of mantle material from one spreading axis into the other. The Terceira <span class="hlt">Rift</span> represents a unique oceanic <span class="hlt">rift</span> <span class="hlt">system</span> situated within the thickened, relatively old oceanic lithosphere and thus exhibits both oceanic and continental features.</p> <div class="credits"> <p class="dwt_author">Beier, Christoph; Haase, Karsten M.; Abouchami, Wafa; Krienitz, Marc-S.; Hauff, Folkmar</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">155</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2003LPI....34.1541H"> <span id="translatedtitle">The Thaumasia "<span class="hlt">Rift</span>", Mars -- Is It a <span class="hlt">Rift</span>?</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">We describe the morphology of a large and complex graben structure in the western Thaumasia region (the Thaumasia graben or "<span class="hlt">rift</span>"). We consider fault geometries, determine extension, and discuss shortly possible models for its origin.</p> <div class="credits"> <p class="dwt_author">Hauber, E.; Kronberg, P.</p> <p class="dwt_publisher"></p> <p class="publishDate">2003-03-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">156</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3542179"> <span id="translatedtitle">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> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary"><span class="hlt">Rift</span> Valley fever (RVF), a mosquito-borne zoonosis, is a major public health and veterinary problem in sub-Saharan Africa. Surveillance to monitor mosquito populations during the inter-epidemic period (IEP) and viral activity in these vectors is critical to informing public health decisions for early warning and control of the disease. Using a combination of field bioassays, electrophysiological and chemical analyses we demonstrated that skin-derived aldehydes (heptanal, octanal, nonanal, decanal) common to RVF virus (RVFV) hosts including sheep, cow, donkey, goat and human serve as potent attractants for RVFV mosquito vectors. Furthermore, a blend formulated from the four aldehydes and combined with CO2-baited CDC trap without a light bulb doubled to tripled trap captures compared to control traps baited with CO2 alone. Our results reveal that (a) because of the commonality of the host chemical signature required for attraction, the host-vector interaction appears to favor the mosquito vector allowing it to find and opportunistically feed on a wide range of mammalian hosts of the disease, and (b) the sensitivity, specificity and superiority of this trapping <span class="hlt">system</span> offers the potential for its wider use in surveillance programs for RVFV mosquito vectors especially during the IEP.</p> <div class="credits"> <p class="dwt_author">Tchouassi, David P.; Sang, Rosemary; Sole, Catherine L.; Bastos, Armanda D. S.; Teal, Peter E. A.; Borgemeister, Christian; Torto, Baldwyn</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">157</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009AGUFM.V13E2076E"> <span id="translatedtitle">Geochemistry of 24 Ma Basalts from Northeast Egypt: Implications for Small-Scale Convection Beneath the East African <span class="hlt">Rift</span> <span class="hlt">System</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Basalts ~24 Ma in the Cairo-Suez and Fayyum districts of NE Egypt represent the youngest and northernmost lavas potentially associated with the initiation of <span class="hlt">rifting</span> of the Red Sea. The age of these basalts corresponds to a time period of significant regional magmatism that occurred subsequent to emplacement of 30 Ma flood basalts attributed to the Afar Plume in Ethiopia and Yemen. Beginning ~28 Ma, widespread magmatism occurred across supra-equatorial Africa in Hoggar (Algeria), Tibesti (Chad), Darfur (Sudan), Turkana (Kenya) and Samalat, Bahariya, Quesir and the Sinai Peninsula (Egypt) (e.g. Allegre et al., 1981; Meneisy, 1990; Baldridge et al., 1991; Wilson and Guiraud, 1992; Furman et al., 2006; Lucassen et al., 2008). Available geochemical and isotopic data indicate that Hoggar and Darfur basalts are similar to Turkana lavas, although no direct link between the N African lavas and the Kenya Plume has been made. New geochemical data on the NE Egyptian basalts provide insight into the thermochemical, isotopic, and mineralogical characteristics of the mantle beneath the region in which they were emplaced. The basalts are subalkaline with OIB-like incompatible trace element abundances and homogeneous major element, trace element and isotopic geochemistry. They display relatively flat ITE patterns, with notable positive Pb and negative P anomalies. Isotopic (143Nd/144Nd = 0.51274-0.51285, 87Sr/86Sr = 0.7049-0.7050) and trace element signatures (Ce/Pb = 16-22, Ba/Nb = 9-14, and La/Nb = 0.9-1.0) are consistent with melting of a sub-lithospheric source that has been slightly contaminated by continental crust during ascent and emplacement. The Pb isotopic ratios (206Pb/204Pb = 18.53-18.62, 207Pb/204Pb = 15.59-15.64, and 208Pb/204Pb = 38.80-39.00) in the Egyptian basalts are close to the range of those found in the 30 Ma Ethiopian flood basalts, which are distinct from the more highly radiogenic, high-? type signature seen in basalts from Turkana, Darfur, and Hoggar. However, measured 207Pb/204Pb and 87Sr/86Sr values are higher than those observed in the Ethiopian flood basalts (Pik et al., 1999) and suites from the Red Sea and Gulf of Aden (Schilling et al., 1992; Volker and McCulloch, 1993; Volker et al., 1997), consistent with trace element evidence of crustal contamination. We aim to develop a broad framework for understanding tectono-magmatic activity throughout northern Africa since the Miocene. The NE Egyptian basalts show evidence of both lithospheric and sublithospheric contributions and represent a time period that is critical to ongoing debate surrounding the relationship between shallow magmatism, crustal extension, and deep mantle processes exemplified by the features within and beneath the African Plate. A plausible model for the widespread volcanism during the early Miocene is that each local magmatic event was related to small scale convection rising above a plume or plumes.</p> <div class="credits"> <p class="dwt_author">Endress, C. A.; Furman, T.; Ali Abu El-Rus, M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">158</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012EGUGA..14.4862B"> <span id="translatedtitle">Numerical Models of Multi-Velocity <span class="hlt">Rift</span> Evolution</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Numerical models are a useful tool to combine present-day knowledge on plate kinematics and lithosphere rheology in order to reveal the complex relations between deformation modes, margin asymmetry and crustal hyperextension. We investigate how long <span class="hlt">rift</span> duration and distinct successive extensional velocities influence lithospheric localization and <span class="hlt">final</span> margin geometry. Our scenarios are computed using a thermo-mechanical, finite element model that includes elasto-visco-plastic rheology and a free surface. The model allows for high resolution of 1 km in a 2d setup with 500 km width and 200 km depth range. We highlight the importance of strain hardening for slow <span class="hlt">rifting</span> (~ 5 mm/yr full extension velocity) where cooling of uplifted mantle material promotes continuous lateral migration of the <span class="hlt">rift</span> center. Despite initially symmetric extension, strain hardening can lead both to significant late <span class="hlt">rift</span> asymmetry and to crustal hyperextension. We use our model to understand the South Atlantic conjugate margin geometries. We thereby build upon a new plate kinematic model for the South Atlantic <span class="hlt">rift</span> which integrates time-dependent information on crustal deformation within a global self-consistent plate rotation framework. Here, the intial continental separation between South America and Africa starts in the Early Cretaceous at low velocities, controlled by African intracontinental <span class="hlt">rifting</span>. After 20-25 Ma of <span class="hlt">rifting</span>, loss of lithospheric strength in the Equatorial Atlantic domain results in a significant increase in extensional velocities and a change in extensional direction from 120 Ma onwards. We investigate the impact of this multi-velocity extension history on the spatio-temporal margin evolution and compare our results with conjugate margin cross-sections at representative locations in the South Atlantic. We couple observations on continental extension from global scale plate tectonic models with high resolution, thermo-mechanical models of lithosphere deformation. This approach offers a powerful way of converging to robust regional tectonic models and link plate-scale kinematics to lithospheric deformation modeling and smaller scale tectonics analysis.</p> <div class="credits"> <p class="dwt_author">Brune, S.; Heine, C.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-04-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">159</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/1989E%26PSL..94..353P"> <span id="translatedtitle">Timing of the volcanism of the southern Kivu province: implications for the evolution of the western branch of the East African <span class="hlt">Rift</span> <span class="hlt">system</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">New K-Ar datings of a large rock sampling from the South Kivu volcanic province (Zaire, Rwanda, Burundi) are reported. No ages older than 10 Ma have been obtained. This result contrasts with older assumptions and puts severe constraints on the relations between volcanism and <span class="hlt">rift</span> evolution. From 10 to 7.5 Ma tholeiitic volcanism predominates corresponding to an episode of fissural eruptions; from 7.5 to 5 Ma alkali basalts and their differentiates are mainly erupted in localized <span class="hlt">rifts</span>. A culmination of activity occurs between 6.0 and 5.5 Ma ago. Pleistocene alkalic volcanism is restricted to localized areas. The transition from tholeiites to alkali-basaltic volcanism dated around 7.5 Ma would correspond to a major <span class="hlt">rifting</span> phase which corresponds with the initiation of Lake Kivu Basin formation. The distribution of tholeiitic rocks in the central part of the <span class="hlt">rift</span>, and predominantly alkalic rocks along the western active border fault, strengthens the idea that the former are associated with tension, the latter with vertical, possibly also strike-slip movements. Volcanism in the Western <span class="hlt">Rift</span> is restricted to areas where tension occurs in a zone which is located between two zones of strike-slip. In the South Kivu area normal faults intersect strike-slip faults and this seems to have determined the location of volcanic activity. Magma formation is considered to be related with shear heating combined with adiabatic decompression in ascending diapirs. This implies heating at the lithosphere-asthenosphere boundary as a result of extension. Generation of tholeiitic or alkalic magmas is connected with the variable ascent velocity of mantle diapirs or with variable shear heating along the shear zone. Changes in both magma composition and intensity of volcanic activity with time are considered to be related to major phases of <span class="hlt">rift</span> evolution.</p> <div class="credits"> <p class="dwt_author">Pasteels, P.; Villeneuve, M.; de Paepe, P.; Klerkx, J.</p> <p class="dwt_publisher"></p> <p class="publishDate">1989-09-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">160</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012GeCoA..89...10D"> <span id="translatedtitle">Os, Nd, O and S isotope constraints on country rock contamination in the conduit-related Eagle Cu-Ni-(PGE) deposit, Midcontinent <span class="hlt">Rift</span> <span class="hlt">System</span>, Upper Michigan</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Eagle Cu-Ni-(PGE) deposit is hosted by mafic to ultramafic intrusive rocks associated with the Marquette-Baraga dike swarm in northern Michigan. Sulfide mineralization formed in a conduit <span class="hlt">system</span> during early stages in the development of the ˜1.1 Ga Midcontinent <span class="hlt">Rift</span> <span class="hlt">System</span>. The conduit environment represents a prime location for melt-rock interaction. In order to better assess the extent of country rock contamination in the Eagle <span class="hlt">system</span>, a combined trace element, Nd, Os, O and S isotope study of country rocks, sulfide-bearing igneous rocks and massive sulfide was undertaken.Both the Eagle and the weakly mineralized East Eagle intrusion show trace element patterns that are similar to those of picritic basalts that formed during early stages of <span class="hlt">rift</span> development. The trace element, Os, Nd, and O isotopic values of the igneous rocks are consistent with <5% of bulk contamination by Paleoproterozoic and Archean country rocks. Both the Re-Os and Sm-Nd <span class="hlt">system</span> provide isochrons that are in agreement with the 1107 Ma U-Pb baddeleyite age of the intrusive rocks. Calculated ?Os(1100) and \\z.epsivNd(1100) values for the magmas are +34 and -2. ?18O values of pyroxene in feldspathic pyroxenite range from 6.5‰ to 6.6‰ and provide the only indication that bulk contamination may locally have exceeded 20%. Sulfur isotopic values of disseminated and massive sulfide in the Eagle intrusion range from 0.3‰ to 4.6‰. The ?34S values are much lower than those that characterize most of the country rocks, but could still be indicative of a contribution of S from country rocks of up to ˜50%. ?33S values of the disseminated and massive sulfides range from -0.10‰ to 0.09‰ indicating a source in Paleoproterozoic country rocks. Semi-massive sulfide in the Eagle deposit has ?34S values between 2.2‰ and 5.3‰, and ?33S values show a broad range between -0.86‰ and 0.86‰ indicating a major contribution from an Archean source. Isotopic data from the Eagle deposit strongly indicate that multiple sources of sulfur were involved in the generation of the Ni-Cu-(PGE) mineralization, and magmas which traversed variable paths through the mantle and crust were focused and utilized the same conduit at the level of the Eagle deposit. Our results emphasize the fact that the sulfur isotopic values of immediate country rocks may not be appropriate as end-member values for mixing calculations; sulfur derivation from deeper in the conduit <span class="hlt">system</span> may have involved rocks with very different sulfur isotope ratios. In addition, sulfur isotopic exchange reactions between passing magma and accumulated crystals or sulfide liquid in the conduit may have led to decreased sulfur isotope variability and ?34S values near those of mantle sulfur.</p> <div class="credits"> <p class="dwt_author">Ding, Xin; Ripley, Edward M.; Shirey, Steven B.; Li, Chusi</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-07-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_7");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" 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showDiv("page_24");' href="#">24</a> <a onClick='return showDiv("page_25");' href="#">25</a> </span> </span> <a id="NextPageLink" onclick='return showDiv("page_10");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">161</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2006Tecto..25.1007B"> <span id="translatedtitle">Fault reactivation and <span class="hlt">rift</span> localization: Northeastern Gulf of Aden margin</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Gulf of Aden and the Sheba spreading ridge (Gulf of Aden) forms the southern boundary of the Arabian Plate. Its orientation (075°E) and its kinematics (about 030°E divergence) are interpreted as the result of an oblique <span class="hlt">rifting</span>. In this contribution, a field study in the northeastern Gulf of Aden allows us to confirm the Oligo-Miocene synrift directions of extension and to precise the normal fault network geometry. The synrift extensions are 020°E and 160°E (possibly in this chronological order); the normal faults strike 070°E, 090°E, and 110°E. The results show that some characteristics are consistent with oblique <span class="hlt">rifting</span> analogue models, while some others are not. Especially, fault reactivation of Mesozoic structures is shown to have occurred significantly at the beginning and during <span class="hlt">rifting</span>. These data are therefore compared to analogue models of oblique reactivation, and this comparison demonstrates that fault reactivation played a key role during the early stage of the Gulf of Aden <span class="hlt">rifting</span>. <span class="hlt">Finally</span>, scenarios of the lithospheric evolution during the eastern Gulf of Aden opening (preexisting weaknesses in the lithosphere or not) are discussed to better constrain the deformation history of the northern margin. Especially, we show that <span class="hlt">rift</span> localization processes may imply stress rotations through time.</p> <div class="credits"> <p class="dwt_author">Bellahsen, N.; Fournier, M.; D'Acremont, E.; Leroy, S.; Daniel, J. M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-02-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">162</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012Tecto..31.2009G"> <span id="translatedtitle">Low-temperature evolution of the Morondava <span class="hlt">rift</span> basin shoulder in western Madagascar: An apatite fission track study</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The evolution of the <span class="hlt">rift</span> shoulder and the sedimentary sequence of the Morondava basin in western Madagascar was mainly influenced by a Permo-Triassic continental failed <span class="hlt">rift</span> (Karroo <span class="hlt">rift</span>), and the early Jurassic separation of Madagascar from Africa. Karroo deposits are restricted to a narrow corridor along the basement-basin contact and parts of this contact feature a steep escarpment. Here, apatite fission track (AFT) analysis of a series of both basement and sediment samples across the escarpment reveals the low-temperature evolution of the exhuming Precambrian basement in the <span class="hlt">rift</span> basin shoulder and the associated thermal evolution of the sedimentary succession. Seven basement and four Karroo sediment samples yield apparent AFT ages between ˜330 and ˜215 Ma and ˜260 and ˜95 Ma, respectively. Partially annealed fission tracks and thermal modeling indicate post-depositional thermal overprinting of both basement and Karroo sediment. Rocks presently exposed in the <span class="hlt">rift</span> shoulder indicate temperatures of >60°C associated with this reheating whereby the westernmost sample in the sedimentary plain experienced almost complete resetting of the detrital apatite grains at temperatures of about ˜90-100°C. The younging of AFT ages westward indicates activity of faults, re-activating inherited Precambrian structures during Karroo sedimentation. Furthermore, our data suggest onset of <span class="hlt">final</span> cooling/exhumation linked to (1) the end of Madagascar's drift southward relative to Africa during the Early Cretaceous, (2) activity of the Marion hot spot and associated Late Cretaceous break-up between Madagascar and India, and (3) the collision of India with Eurasia and subsequent re-organization of spreading <span class="hlt">systems</span> in the Indian Ocean.</p> <div class="credits"> <p class="dwt_author">Giese, JöRg; Seward, Diane; Schreurs, Guido</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-04-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">163</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=203219"> <span id="translatedtitle">An automated GIS/remotely sensed early warning <span class="hlt">system</span> to detect elevated populations of vectors of <span class="hlt">Rift</span> Valley fever, a mosquito-borne emerging virus threat</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p class="result-summary">Mosquito transmitted infectious diseases, like eastern equine encephalitis (EEE), <span class="hlt">Rift</span> Valley fever (RVF), and West Nile virus (WNV), pose an international threat to animal and human health. An introduction of RVF into the U.S. would severely impact wild ungulate populations and the beef and dairy ...</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">164</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/21295425"> <span id="translatedtitle">[<span class="hlt">Rift</span> Valley fever].</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary"><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. PMID:21295425</p> <div class="credits"> <p class="dwt_author">Pépin, M</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-02-03</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">165</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/1023141"> <span id="translatedtitle">DCE Bio Detection <span class="hlt">System</span> <span class="hlt">Final</span> Report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">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> <div class="credits"> <p class="dwt_author">Lind, Michael A.; Batishko, Charles R.; Morgen, Gerald P.; Owsley, Stanley L.; Dunham, Glen C.; Warner, Marvin G.; Willett, Jesse A.</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">166</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/60251492"> <span id="translatedtitle">Ceramic regenerator <span class="hlt">systems</span> development program. <span class="hlt">Final</span> report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">This is the <span class="hlt">final</span> report for the NASA\\/Ford Ceramic Regenerator <span class="hlt">Systems</span> Development Program. It describes all of the results obtained in this program, which started October 1, 1976 and was completed December 31, 1979. Tasks within this program included: core durability testing at 800°C (1472°F); core durability testing at 1000°C (1832°F); material screening tests; aerothermodynamic performance; design studies of advanced</p> <div class="credits"> <p class="dwt_author">C. A. Fucinari; C. J. Rahnke; V. D. N. Rao; J. K. Vallance</p> <p class="dwt_publisher"></p> <p class="publishDate">1980-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">167</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010AGUFM.T22C..06G"> <span id="translatedtitle">Faulting processes during early-stage <span class="hlt">rifting</span>: seismicity analysis of the 2009-2010 Northern Malawi earthquake sequence</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">One of the most poorly understood aspects of the <span class="hlt">rifting</span> process is early-stage <span class="hlt">rift</span> initiation. Core questions concern how deformation nucleates and evolves throughout the lithosphere, both along strike and through time, and how magma participates in extension. In December 2009, a rare sequence of earthquakes initiated within the nascent, southern portion of the East African <span class="hlt">Rift</span> (EAR) <span class="hlt">system</span> in northern Malawi’s Karonga district; eleven earthquakes with Mw > 4.5 occurred over a 12-day period. The largest events range from Mw 5.8-6.0, and appear to occur on one or more shallow normal faults located in the hanging wall well above the primary <span class="hlt">rift</span> border fault. They thus differ from nearly all other moderate-size earthquakes within the Western <span class="hlt">Rift</span> of the EAR, which appear to be on major border faults, and they imply a critical role for hanging-wall faults in accommodating early-stage <span class="hlt">rifting</span>. Using teleseismic and regional recordings of the largest events, and recordings of aftershocks from a temporary (4-month) local network comprising six stations, we evaluate the nature of faulting during early-stage <span class="hlt">rifting</span>. The zeroth-order (automated) detection and location of over ~1000 aftershocks recorded on our temporary network between Jan-May 2010 is consistent with faulting in the hanging wall, with the bulk of the seismicity suggesting a west-dipping normal fault shallower than about 10 km. Surface breaks in the Karonga region have vertical offsets up to ~0.65 m, and are continuous along strike for up to 17 km. However, there is a broad distribution of epicenters extending both north and south of Karonga, as well as events significantly deeper than 10 km. The spatial distribution of events is strongly suggestive of multiple faults interacting to produce the observed deformation. More speculatively, the presence of events at depths > 25 km, and the abundant distribution of events up into the Rungwe volcanic province in southern Tanzania hint at either a potential deep magmatic role in these events, and/or possible interaction between secondary faults and the border fault. <span class="hlt">Finally</span>, the rate of earthquake occurrence shows a secondary burst of activity that is inconsistent with a simple Omori’s Law decay of aftershocks. We are currently evaluating these initial findings with a comprehensive relocation and moment-tensor analysis of the sequence.</p> <div class="credits"> <p class="dwt_author">Gaherty, J. B.; Shillington, D. J.; Shuler, A. E.; Kapanje, W.; Chindandali, P.; Nooner, S. L.; Ebinger, C. J.; Nyblade, A.; Kalindekafe, L.; Pritchard, M. E.; Scholz, C. A.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">168</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/799225"> <span id="translatedtitle">Field Studies of Geothermal Reservoirs Rio Grande <span class="hlt">Rift</span>, New Mexico</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">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> <div class="credits"> <p class="dwt_author">James C Witcher</p> <p class="dwt_publisher"></p> <p class="publishDate">2002-07-30</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">169</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/1986E%26PSL..77..176M"> <span id="translatedtitle">The geometry of propagating <span class="hlt">rifts</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">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> <div class="credits"> <p class="dwt_author">McKenzie, Dan</p> <p class="dwt_publisher"></p> <p class="publishDate">1986-03-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">170</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/54935431"> <span id="translatedtitle">Tectonics of the Jemez lineament in the Jemez Mountains and Rio Grande <span class="hlt">rift</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The Jemez lineament is a NE trending crystal flaw that controlled volcanism and tectonism in the Jemez Mountains and the Rio Grande <span class="hlt">rift</span> zone. The fault <span class="hlt">system</span> associated with the lineament in the <span class="hlt">rift</span> zone includes, from west to east, the Jemez fault zone southwest of Valles-Toledo caldera complex, a series of NE trending faults on the resurgent dome in</p> <div class="credits"> <p class="dwt_author">M. J. Aldrich</p> <p class="dwt_publisher"></p> <p class="publishDate">1986-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">171</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40732586"> <span id="translatedtitle">Petrogenesis of silicic peralkaline rocks in the Ethiopian <span class="hlt">rift</span>: Geochemical evidence and volcanological implications</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Major, trace element and isotopic data for mafic to peralkaline silicic volcanic rocks from the northern sector of the main Ethiopian <span class="hlt">rift</span> are discussed with the aim of placing constraints on processes of magma genesis and evolution and to present models for magma plumbing <span class="hlt">systems</span> of <span class="hlt">rift</span> volcanoes. Basalts straddle the subalkaline–alkaline boundary and exhibit important variations of incompatible element</p> <div class="credits"> <p class="dwt_author">A. Peccerillo; C. Donati; A. P. Santo; A. Orlando; G. Yirgu; D. Ayalew</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">172</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.springerlink.com/index/27nv4cgy77wufu1h.pdf"> <span id="translatedtitle"><span class="hlt">Rifting</span>, recurrent landsliding and Miocene structural reorganization on NW-Tenerife (Canary Islands)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">We studied mechanisms of structural destabilization of ocean island flanks by considering the linkage between volcano construction and volcano destruction, exemplified by the composite Teno shield volcano on Tenerife (Canary Islands). During growth, Tenerife episodically experienced giant landslides, genetically associated with <span class="hlt">rifting</span> and preferentially located between two arms of a three-armed <span class="hlt">rift</span> <span class="hlt">system</span>. The deeply eroded late Miocene Teno massif</p> <div class="credits"> <p class="dwt_author">T. Walter; H.-U. Schmincke</p> <p class="dwt_publisher"></p> <p class="publishDate">2002-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">173</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/48907784"> <span id="translatedtitle">Contrasted styles of <span class="hlt">rifting</span> in the eastern Gulf of Aden: A combined wide-angle, multichannel seismic, and heat flow survey</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Continental <span class="hlt">rifts</span> and passive continental margins show fundamental along-axis segmentation patterns that have been attributed to one or a number of different processes: extensional fault geometry, variable stretching along strike, preexisting lithospheric compositional and structural heterogeneities, oblique <span class="hlt">rifting</span>, and the presence or absence of eruptive volcanic centers. The length and width scales of the <span class="hlt">rift</span> stage fault-bounded basin <span class="hlt">systems</span> change</p> <div class="credits"> <p class="dwt_author">Sylvie Leroy; Francis Lucazeau; Elia d'Acremont; Louise Watremez; Julia Autin; Stéphane Rouzo; Nicolas Bellahsen; Christel Tiberi; Cynthia Ebinger; Marie-Odile Beslier; Julie Perrot; Philippe Razin; Frédérique Rolandone; Heather Sloan; Graham Stuart; Ali Al Lazki; Khalfan Al-Toubi; François Bache; Alain Bonneville; Bruno Goutorbe; Philippe Huchon; Patrick Unternehr; Khaled Khanbari</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">174</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010E%26PSL.297..667M"> <span id="translatedtitle">Stress re-orientation along zones of weak fabrics in <span class="hlt">rifts</span>: An explanation for pure extension in ‘oblique’ <span class="hlt">rift</span> segments?</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Cenozoic East African <span class="hlt">Rift</span> <span class="hlt">System</span> (EAR) displays strong interaction between <span class="hlt">rift</span> faults and zones of weakness in Precambrian basement and Late Carboniferous-Permian Karroo <span class="hlt">rifts</span>. Assuming E-W regional extension, NW-SE and NE-SW trending <span class="hlt">rift</span> segments following older zones of weakness are expected to show oblique extensional or transtensional displacement. Yet, the earthquake focal mechanism-derived modern maximum horizontal stress (Shmax) pattern in the Western Branch of the EAR displays similar orientations to dominant foliation direction in Proterozoic orogenic belts. The oblique segments are undergoing almost pure extension. Localized stress deflections near zones of strength anisotropy are commonly described in studies of geomechanics, in-situ stresses and fracture patterns. The correspondence between foliation and Shmax direction in the Western Branch suggests re-orientation of stress at a larger scale than has previously been recognized. The stress guide effect appears best developed in the Ubendian Belt-Rukwa <span class="hlt">Rift</span> where the Shmax direction from the regional N-S direction to a NW-SE trend and NW-SE trending foliations are consistently steeply dipping. However, this effect is considered only one of a number of possible causes of stress deflection in the East African <span class="hlt">Rift</span>. Precambrian basement foliation is not oriented consistently enough to re-orient stress on a large-scale everywhere (particularly the Kenya <span class="hlt">Rift</span>). The effects of stress rotation along oblique fabrics are: 1) faults normally predicted to exhibit oblique slip are actually near pure dip-slip, 2) faults along oblique trends can be optimally oriented with respect to the (local) stress field, and develop in a zone of reduced cohesive shear strength (with respect to isotropic rocks), 3) where foliations are inclined from vertical the maximum principal stress will be similarly inclined leading to initiation of extensional faults at angles considerably lower than 60°, and 4) faults will strike parallel to the foliation but cross-cut foliations in cross-section.</p> <div class="credits"> <p class="dwt_author">Morley, C. K.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-09-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">175</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010Tecto..29.5008G"> <span id="translatedtitle">Kinematic and thermal evolution of the Moroccan <span class="hlt">rifted</span> continental margin: Doukkala-High Atlas transect</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Atlantic passive margin of Morocco developed during Mesozoic times in association with the opening of the Central Atlantic and the Alpine Tethys. Extensional basins formed along the future continental margin and in the Atlas <span class="hlt">rift</span> <span class="hlt">system</span>. In Alpine times, this <span class="hlt">system</span> was inverted to form the High and Middle Atlas fold-and-thrust belts. To provide a quantitative kinematic analysis of the evolution of the <span class="hlt">rifted</span> margin, we present a crustal section crossing the Atlantic margin in the region of the Doukkala Basin, the Meseta and the Atlas <span class="hlt">system</span>. We construct a post-<span class="hlt">rift</span> upper crustal section compensating for Tertiary to present vertical movements and horizontal deformations, and we conduct numerical modeling to test quantitative relations between amounts and distribution of thinning and related vertical movements. <span class="hlt">Rifting</span> along the transect began in the Late Triassic and ended with the appearance of oceanic crust at 175 Ma. Subsidence, possibly related to crustal thinning, continued in the Atlas <span class="hlt">rift</span> in the Middle Jurassic. The numerical models confirm that the margin experienced a polyphase <span class="hlt">rifting</span> history. The lithosphere along the transect preserved some strength throughout <span class="hlt">rifting</span> with the Effective Elastic Thickness corresponding to an isotherm of 450°C. A mid-crustal level of necking of 15 km characterized the pre-<span class="hlt">rift</span> lithosphere.</p> <div class="credits"> <p class="dwt_author">Gouiza, M.; Bertotti, G.; Hafid, M.; Cloetingh, S.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-10-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">176</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012JVGR..239...49D"> <span id="translatedtitle">Hypogene and supergene alteration of the zeolite-bearing pyroclastic deposits at Tell Rimah, Jordan, and <span class="hlt">rift</span>-related processes along the Dead-Sea-Transform Fault <span class="hlt">System</span> during the Quaternary</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The boundary between the Arabian and African plates, is marked in the Middle East by one of the most prominent deep-seated lineamentary structures, called the Dead-Sea-Transform Fault <span class="hlt">System</span> (DSTFS). Structural and mineralogical processes related to the DSTFS were correlated with equivalent processes leading to the alteration of pyroclastic deposits of alkali-olivine basaltic to nepheline basaltic composition which formed during a time span of less than 0.5 Ma. The large deposit of Tell Rimah, Jordan, is operated for the exploitation of zeolites, tuffs, and as pozzolana raw material. Four discrete stages of mineralizations have been distinguished from each other within these volcanic-hosted mineral deposits.(1) Hypogene syneruptive alteration of pyroclastic rocks produced siliceous gels ("allophane"), smectite, analcime, and phillipsite in vesicles when the groundwater level was low in the <span class="hlt">rift</span> basin of the DSTFS. The lake-level lowstand caused the fluid <span class="hlt">system</span> in the pyroclastic cone to become self-sufficient and it has been considered as a closed hydrothermal <span class="hlt">system</span>. (2) Periods of tectonic and magmatic quiescence grinded the detrital sedimentation in the <span class="hlt">rift</span> basin to a halt, while triggering a supergene alteration in the eruptive cones on the adjacent Arabian Plate. (3) Epigenetic alteration affected the pyroclastic rocks in the distal part of the DSTFS as a result of a rising water level. The water gradually filled the pore space of the permeable pyroclastic deposits almost to completeness and caused meniscus and blocky cements of calcite, phillipsite and chabazite to develop. In the <span class="hlt">rift</span> basin, contemporaneously with the alteration of the pyroclastic rocks, freshwater limestones formed on calcareous bedrocks. Ba and Mn minerals in these freshwater limestones were supplied by subaquatic brines. Subsequently, a drastic lowering of the lake water level in the DSTFS converted the <span class="hlt">system</span> of subaquatic freshwater limestones into subaerial tufa and travertine. As long as the basal parts of the pyroclastic units at Tell Rimah were in the reaches of the saline groundwaters, calcite and faujasite developed in the pyroclastic host rocks. (4) Another lake level lowstand within the <span class="hlt">rift</span> basin caused the pyroclastic host rocks to get emerged and forced zeolite-carbonate mineralization in the tuffs to a complete stillstand. Hypogene and supergene alteration in these phreatomagmatic-strombolian pyroclastic cones of the Pleistocene x were correlated with lake high- and lowstands in the adjacent <span class="hlt">rift</span> basin along the DSTFS.The results obtained by current tectono-morphological studies of the <span class="hlt">rift</span>-related alteration of pyroclastic rocks along the DSTFS may also be applied to basin-and-swell-topographies elsewhere in the world. The current studies involved microscopy supplemented by SEM-EDX, X-ray diffraction analysis, mid (MIR) and far (FIR) infrared spectroscopy. Major and trace elements were analyzed by X-ray fluorescence spectrometry (XRF). C- and O isotope analyses were conducted on carbonate minerals, which were also targeted on by radiocarbon dating.</p> <div class="credits"> <p class="dwt_author">Dill, H. G.; Techmer, A.; Botz, R.; Dohrmann, R.; Kaufhold, S.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-09-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">177</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/376401"> <span id="translatedtitle">Facilities management <span class="hlt">system</span> (FMS). <span class="hlt">Final</span> report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">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> <div class="credits"> <p class="dwt_author">NONE</p> <p class="dwt_publisher"></p> <p class="publishDate">1992-04-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">178</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/376373"> <span id="translatedtitle">Facilities management <span class="hlt">system</span> (FMS). <span class="hlt">Final</span> report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">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> <div class="credits"> <p class="dwt_author">NONE</p> <p class="dwt_publisher"></p> <p class="publishDate">1992-04-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">179</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/6927518"> <span id="translatedtitle">Solar energy <span class="hlt">system</span>, Baltimore County Jail, Towson, Maryland. <span class="hlt">Final</span> report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The Baltimore County Jail solar <span class="hlt">system</span> incorporates four independent piping <span class="hlt">systems</span>: (1) glycol loop <span class="hlt">system</span>; (2) solar water <span class="hlt">system</span>; (3) chilled water <span class="hlt">system</span>; and (4) domestic cold and hot water <span class="hlt">system</span>. This <span class="hlt">final</span> report includes: <span class="hlt">final</span> <span class="hlt">system</span> description; construction costs; as-build drawings; acceptance test; control drawings; and product information.</p> <div class="credits"> <p class="dwt_author">Not Available</p> <p class="dwt_publisher"></p> <p class="publishDate">1984-02-20</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">180</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/1993AAS...183.4502I"> <span id="translatedtitle">The IUE <span class="hlt">Final</span> Archive Processing <span class="hlt">System</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The IUE Project has begun the task of reprocessing all IUE data using significantly enhanced reduction algorithms and calibrations. In order to perform this task in a timely, reliable manner, we have developed the IUE <span class="hlt">Final</span> Archive Processing <span class="hlt">System</span>. The <span class="hlt">system</span> runs on a DECstation 5000, using Fortran software embedded in portable MIDAS. The processing queue is driven by a commercial relational database. The database interface allows the <span class="hlt">system</span> to access the enhanced IUE database, which is resident on a second DECstation 5000 (see poster by Levay et al.). The <span class="hlt">system</span> runs automatically, with little operator intervention. Built-in quality assurance software detects virtually all input or processing problems. In addition, a fraction of the images, including all those with quality assurance warnings, are screened by the staff. The screening <span class="hlt">system</span>, known as the Post-Production Verification (PPV) <span class="hlt">system</span>, uses a widget-based graphics user interface written in IDL. It allows one to display and inspect the MIDAS and FITS files, review the FITS headers and other text files, and record the results in the IUE database. Images which have passed quality assurance are then delivered to NASA's National Space Science Data Center, which makes the data available to the astronomical community. This work has been supported under NASA contract NAS5-31230 to Computer Sciences Corp.</p> <div class="credits"> <p class="dwt_author">Imhoff, C. L.; Dunn, N.; Fireman, G. F.; Levay, K. L.; Meylan, T.; Nichols, J.; Michalitsianos, A.</p> <p class="dwt_publisher"></p> <p class="publishDate">1993-12-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_8");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a onClick='return showDiv("page_3");' href="#">3</a> <a 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onClick='return showDiv("page_12");' href="#">12</a> <a onClick='return showDiv("page_13");' href="#">13</a> <a onClick='return showDiv("page_14");' href="#">14</a> <a onClick='return showDiv("page_15");' href="#">15</a> <a onClick='return showDiv("page_16");' href="#">16</a> <a onClick='return showDiv("page_17");' href="#">17</a> <a onClick='return showDiv("page_18");' href="#">18</a> <a onClick='return showDiv("page_19");' href="#">19</a> <a onClick='return showDiv("page_20");' href="#">20</a> <a onClick='return showDiv("page_21");' href="#">21</a> <a onClick='return showDiv("page_22");' href="#">22</a> <a onClick='return showDiv("page_23");' href="#">23</a> <a onClick='return showDiv("page_24");' href="#">24</a> <a onClick='return showDiv("page_25");' href="#">25</a> </span> </span> <a id="NextPageLink" onclick='return showDiv("page_11");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">181</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2001NIMPA.464..410M"> <span id="translatedtitle">Neutronic calculations for a <span class="hlt">final</span> focus <span class="hlt">system</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">For heavy-ion fusion and for ``liquid-protected'' reactor designs such as HYLIFE-II (Moir et al., Fusion Technol. 25 (1994); HYLIFE-II-Progress Report, UCID-21816, 4-82-100), a mixture of molten salts made of F10, Li6, Li7, Be9 called flibe allows highly compact target chambers. Smaller chambers will have lower costs and will allow the <span class="hlt">final</span>-focus magnets to be closer to the target with decreased size of the focus spot and of the driver, as well as drastically reduced costs of IFE electricity. Consequently the superconducting coils of the magnets closer to the chamber will suffer higher radiation damage though they can stand only a certain amount of energy deposited before quenching. The scope of our calculations is essentially the total energy deposited on the magnetic lens <span class="hlt">system</span> by fusion neutrons and induced /?-rays. Such a study is important for the design of the <span class="hlt">final</span> focus <span class="hlt">system</span> itself from the neutronic point of view and indicates some guidelines for a design with six magnets in the beam line. The entire chamber consists of 192 beam lines to provide access of heavy ions that will implode the pellet. A 3-D transport calculation of the radiation penetrating through ducts that takes into account the complexity of the <span class="hlt">system</span>, requires Monte Carlo methods. The development of efficient and precise models for geometric representation and nuclear analysis is necessary. The parameters are optimized thanks to an accurate analysis of six geometrical models that are developed starting from the simplest. Different configurations are examined employing TART 98 (D.E. Cullen, Lawrence Livermore National Laboratory, UCRL-ID-126455, Rev. 1, November, 1997) and MCNP 4B (Briesmeister (Ed.), Version 4B, La-12625-m, March 1997, Los Alamos National Laboratory): two Monte Carlo codes for neutrons and photons. The quantities analyzed include: energy deposited by neutrons and gamma photons, values of the total fluence integrated on the whole energy range, neutron fluence spectrum, total path length of neutrons in energy, neutron mean free path versus energy. The results of the two codes turned out to be in good agreement with each other for different zones and configurations of the <span class="hlt">system</span>. The source restriction technique gives reliable results as it is proved comparing re-normalized results with results obtained with a 4? source and with sources emitting with different set of solid angles. For this reason, this technique is used in all the six models avoiding other variance reduction techniques. <span class="hlt">Finally</span>, solutions are suggested for optimizing the <span class="hlt">system</span> from the neutronic point of view, with respect to both relative position of the magnets and choice of shielding materials.</p> <div class="credits"> <p class="dwt_author">Mainardi, E.; Premuda, F.; Lee, E.</p> <p class="dwt_publisher"></p> <p class="publishDate">2001-05-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">182</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/24066364"> <span id="translatedtitle">Unique device identification <span class="hlt">system</span>. <span class="hlt">Final</span> rule.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">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. PMID:24066364</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate">2013-09-24</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">183</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012EGUGA..14.5381C"> <span id="translatedtitle">Stress and slip partitioning during oblique <span class="hlt">rifting</span>: comparison between data from the Main Ethiopian <span class="hlt">Rift</span> and laboratory experiments</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Oblique <span class="hlt">rifting</span> in the central and northern Main Ethiopian <span class="hlt">Rift</span> (MER) has resulted in a complex structural pattern characterized by two differently oriented fault <span class="hlt">systems</span>: a set of NE-SW-trending boundary faults and a <span class="hlt">system</span> of roughly NNE-SSW-oriented fault swarms affecting the <span class="hlt">rift</span> floor (Wonji faults). Boundary faults formed oblique to the regional extension vector, likely as a result of the oblique reactivation of a pre-existing deep-seated rheological anisotropy, whereas internal Wonji faults developed sub-orthogonal to the stretching direction. Previous works have successfully reconciled this <span class="hlt">rift</span> architecture and fault distribution with the long-term plate kinematics; however, at a more local scale, fault-slip and earthquake data reveal significant variations in the orientation the minimum principal stress and related fault-slip direction across the <span class="hlt">rift</span> valley. Whereas fault measurements indicate a roughly N95°E extension on the axial Wonji faults, a N105°E to N110°E directed minimum principal stress is observed along boundary faults. Both fault-slip data and analysis of seismicity indicate a roughly pure dip-slip motion on the boundary faults, despite their orientation (oblique to the regional extension vector) should result in an oblique displacement. To shed light on the process driving the variability of data derived from fault-slip (and seismicity) analysis we present crustal-scale analogue models of oblique <span class="hlt">rifting</span>, deformed in a large-capacity centrifuge by using materials and boundary conditions described in several previous modeling works. As in these previous works, the experiments show the diachronous activation of two fault <span class="hlt">systems</span>, boundary and internal, whose pattern strikingly resemble that observed in previous lithospheric-scale modeling, as well as that described in the MER. Internal faults arrange in two different, en-echelon segments connected by a transfer zone where strike-slip displacement dominates. Whereas internal faults develop roughly orthogonal to the extension direction, boundary faults form oblique to the imposed stretching vector: as a group, the faults follow the <span class="hlt">rift</span> trend, controlled by a pre-existing weak anisotropy, but individually they form oblique to both the <span class="hlt">rift</span> margin and the extension vector. Detailed analysis of fault displacements suggest that whereas the average displacement on single internal faults is consistent with the imposed direction of extension, slip on boundary faults does not parallel this direction; the average motion on these faults is orthogonal to the faults, resulting in a roughly pure dip-slip motion. This gives rise to a marked difference in fault-slip direction between internal faults (where slip orientation follow the regional extension) and boundary faults (where displacement is oblique to the "regional" extension). A similar scenario is observed for the reconstructed direction of the minimum principal stress that follows the regional stress field within the <span class="hlt">rift</span> and is re-oriented at <span class="hlt">rift</span> margins. Minor counterclockwise block rotations accommodate the different slip along the different fault <span class="hlt">systems</span>. The model-to-nature striking is striking in terms of fault orientation, stress and slip orientation and its across-axis variations. The analogue models thus allows explaining the across-axis variability observed in natural fault-slip and earthquake data. Modeling results support that boundary faults form in response to a local stress re-orientation imposed by a deep seated anisotropy: their displacement trajectories deviate from those imposed by the regional extension, resulting in a pure dip-slip motion in an overall oblique <span class="hlt">rifting</span> kinematics, as observed in other sectors of the East African <span class="hlt">Rift</span>. Conversely, internal faults -which form later and affect a weaker, more uniform lithosphere- respond directly to the regional extension direction resulting in a fault slip sub-parallel to the Nubia-Somalia motion. Minor counterclockwise block rotations are required to accommodate the difference in slip along the different fault <span class="hlt">systems</span>.</p> <div class="credits"> <p class="dwt_author">Corti, G.; Philippon, M.; Sani, F.; Keir, D.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-04-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">184</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/23823795"> <span id="translatedtitle">Melting during late-stage <span class="hlt">rifting</span> in Afar is hot and deep.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Investigations of a variety of continental <span class="hlt">rifts</span> and margins worldwide have revealed that a considerable volume of melt can intrude into the crust during continental breakup, modifying its composition and thermal structure. However, it is unclear whether the cause of voluminous melt production at volcanic <span class="hlt">rifts</span> is primarily increased mantle temperature or plate thinning. Also disputed is the extent to which plate stretching or thinning is uniform or varies with depth with the entire continental lithospheric mantle potentially being removed before plate rupture. Here we show that the extensive magmatism during <span class="hlt">rifting</span> along the southern Red Sea <span class="hlt">rift</span> in Afar, a unique region of sub-aerial transition from continental to oceanic <span class="hlt">rifting</span>, is driven by deep melting of hotter-than-normal asthenosphere. Petrogenetic modelling shows that melts are predominantly generated at depths greater than 80?kilometres, implying the existence of a thick upper thermo-mechanical boundary layer in a <span class="hlt">rift</span> <span class="hlt">system</span> approaching the point of plate rupture. Numerical modelling of <span class="hlt">rift</span> development shows that when breakup occurs at the slow extension rates observed in Afar, the survival of a thick plate is an inevitable consequence of conductive cooling of the lithosphere, even when the underlying asthenosphere is hot. Sustained magmatic activity during <span class="hlt">rifting</span> in Afar thus requires persistently high mantle temperatures, which would allow melting at high pressure beneath the thick plate. If extensive plate thinning does occur during breakup it must do so abruptly at a late stage, immediately before the formation of the new ocean basin. PMID:23823795</p> <div class="credits"> <p class="dwt_author">Ferguson, D J; Maclennan, J; Bastow, I D; Pyle, D M; Jones, S M; Keir, D; Blundy, J D; Plank, T; Yirgu, G</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-07-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">185</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2004EOSTr..85..500A"> <span id="translatedtitle">The life cycle of continental <span class="hlt">rifting</span> as a focus for U.S.-African scientific collaboration</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">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> <div class="credits"> <p class="dwt_author">Abdelsalam, Mohamed G.; Atekwana, Estella A.; Keller, G. Randy; Klemperer, Simon L.</p> <p class="dwt_publisher"></p> <p class="publishDate">2004-11-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">186</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012EGUGA..1410762J"> <span id="translatedtitle"><span class="hlt">Rifting</span>, heat flux, and water availability beneath the catchment of Pine Island Glacier</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The West Antarctic <span class="hlt">Rift</span> <span class="hlt">System</span> (WARS) is a major <span class="hlt">rift</span> <span class="hlt">system</span> that developed in the Cretaceous and Cenozoic. It forms the lithsopheric cradle for the marine-based, and potentially unstable West Antarctic Ice Sheet (WAIS). Determining the geological boundary conditions beneath the WAIS and in particular geothermal heat flux may help model its response to external climatic forcing. However, in the Amundsen Sea Embayment sector of WAIS, where major glaciers such as Pine Island and Thwaites are rapidly changing today, fundamental properties such as geothermal heat flux to the base of the ice sheet have remained poorly constrained due to sparse geophysical data coverage and the lack of drilling sites. New crustal thickness estimates derived from airborne gravity data (Jordan et al., 2010, GSA Bul.), are interpreted to show a continuation of the WARS beneath Pine Island Glacier, and suggest two phases of continental <span class="hlt">rifting</span> affected this region. Here we explore the impact of continental <span class="hlt">rifting</span> on geothermal heat flux variations and basal water availability beneath Pine Island Glacier. Using 1D thermal models of <span class="hlt">rift</span> evolution, we assess geothermal heat flux configurations resulting from either single or two-phase <span class="hlt">rifting</span> and explore the dependency on the age of <span class="hlt">rifting</span> and pre-<span class="hlt">rift</span> setting. Additionally, 1D glaciological models were implemented to predict the changes in subglacial water distribution created by different <span class="hlt">rifting</span> models. Our modelling reveals that geothermal heat-flux beneath the WAIS is critically sensitive to <span class="hlt">rift</span> age and evolution and has the potential to significantly alter basal conditions if it continued to be active in the Neogene as some recent geological interpretations suggest.</p> <div class="credits"> <p class="dwt_author">Jordan, T. A.; Ferraccioli, F.; Hindmarsh, R. C.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-04-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">187</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009EGUGA..11.3548I"> <span id="translatedtitle">Recent geodynamics and evolution of the Moma <span class="hlt">rift</span>, Northeast Asia.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">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 springs with temperatures up to +20°C are found within the Moma and Selnnyakh basins proper.The crustal inhomogeneity is also reflected in the upper mantle as indicated by a 40° rotation of the Rayleigh wave polarization angle from teleseisms recorded at Tiksi that cross the Moma <span class="hlt">rift</span> <span class="hlt">system</span> as opposed to those that do not. Cenozoic volcanism, chemically similar to basalts and rhyolites from <span class="hlt">rift</span> zones elsewhere is found in the Moma <span class="hlt">rift</span> proper. Balagan-Tas is a basaltic cinder cone which has been dated at 286,000 years based on Ar-Ar dating, while Uraga-Khaya is an undated, presumed Quaternary, rhyolitic dome. All these factors indicate that the Moma <span class="hlt">rift</span> <span class="hlt">system</span> originated as a continental <span class="hlt">rift</span>, probably as an extension of the Arctic (Gakkel) Mid-Ocean Ridge. At the present, however, compressional conditions prevail within the Moma <span class="hlt">rift</span> zone. Seismicity is generally absent from the <span class="hlt">rift</span> basins proper or their margins; most seismicity is concentrated to the southwest of the Moma <span class="hlt">rift</span> basins along major strike-slip fault <span class="hlt">systems</span>. Focal mechanisms of the largest earthquakes in the Chersky Range also all show transpression. Field mapping indicates that the majority of the faults mapped in the field are strike-slip, thrust and reverse faults (86%) with only a small number of normal faults (14%) and that the Cenozoic deposits within the Moma <span class="hlt">rift</span> are intensely folded. Re-leveling surveys conducted along the Indigirka River, which cuts across the Moma <span class="hlt">rift</span> <span class="hlt">system</span>, reveal a moderate rate of presnt-day vertical uplift (up to +4 mm/yr). Thus, the Moma <span class="hlt">rift</span> <span class="hlt">system</span> is no longer acting as a <span class="hlt">rift</span>, but is undergoing transpression. This conclusion is also supported by recent plate motion calculations based on GPS and VLBI data, as well as slip-vectors of earthquakes, which indicates that the Euler pole between North America and Eurasia is located around 68-70°N, near the coast of the Laptev Sea. This places the Moma <span class="hlt">rift</span> <span class="hlt">system</span> in a zone of convergence between North America and Eurasia; this geometry also supports the extrusion of the Okhotsk Sea plate. Poles of ro</p> <div class="credits"> <p class="dwt_author">Imaev, V. S.; Imaeva, L. P.; Kozmin, B. M.; Fujita, K. S.; Mackey, K. G.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-04-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">188</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/48946234"> <span id="translatedtitle">Postspreading <span class="hlt">rifting</span> in the Adare Basin, Antarctica: Regional tectonic consequences</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Extension during the middle Cenozoic (43–26 Ma) in the north end of the West Antarctic <span class="hlt">rift</span> <span class="hlt">system</span> (WARS) is well constrained by seafloor magnetic anomalies formed at the extinct Adare spreading axis. Kinematic solutions for this time interval suggest a southward decrease in relative motion between East and West Antarctica. Here we present multichannel seismic reflection and seafloor mapping data</p> <div class="credits"> <p class="dwt_author">R. Granot; S. C. Cande; J. M. Stock; F. J. Davey; R. W. Clayton</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">189</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.nsf-margins.org/Nuggets_Public/Nuggets_Final/RCL/McClusky_Reilinger_etal_Geodetic_Constraints.pdf"> <span id="translatedtitle">Geodetic constraints on continental <span class="hlt">rifting</span> along the Red Sea</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">We are using the Global Positioning <span class="hlt">System</span> (GPS) to monitor and quantify patterns and rates of tectonic and magmatic deformation associated with active <span class="hlt">rifting</span> of the continental lithosphere and the transition to sea floor spreading in the Red Sea. Broad-scale motions of the Nubian and Arabian plates indicate coherent plate motion with internal deformation below the current resolution of our</p> <div class="credits"> <p class="dwt_author">R. Reilinger; S. McClusky; A. Arrajehi; S. Mahmoud; A. Rayan; W. Ghebreab; G. Ogubazghi; A. Al-Aydrus</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">190</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2008AGUSM.S41A..05T"> <span id="translatedtitle">Continental <span class="hlt">rift</span> zones without Moho uplift</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary"><span class="hlt">Rifting</span> is a fundamental plate tectonic process that creates elongated depressions in the Earth's surface, which become filled with sedimentary and volcanic material, as it is presently observed at the Baikal, East African, Rhine Graben and Rio Grande <span class="hlt">Rift</span> Zones. All <span class="hlt">rifting</span> models predict Moho uplift due to crustal thinning, and reduced seismic velocity in the uppermost mantle due to decompression or heating from the Earth's interior. However, recently acquired data from the presently active Baikal <span class="hlt">Rift</span> zone in Siberia and the failed Dniepr-Donets <span class="hlt">rift</span> zone in Ukraine are examples where there is no Moho topography that can related to the <span class="hlt">rifting</span> process. Further, data from the Kenya <span class="hlt">Rift</span> Zone shows sign of less Moho uplift than expected from the actual extension. At all these <span class="hlt">rift</span> zones, we observe a localized zone in the lower crust which has exceptionally high seismic velocity and is highly reflective. We suggest that <span class="hlt">rift</span> related crustal thinning took place, but the expected Moho up-warp was compensated by magmatic intrusion in the lower crust at the high-velocity zone. This finding has significant implications for modelling of the evolution of sedimentary basins around <span class="hlt">rift</span> structures.</p> <div class="credits"> <p class="dwt_author">Thybo, H.; Lyngsie, S.; Nielsen, C.</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-05-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">191</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2004E%26PSL.223..349D"> <span id="translatedtitle">40Ar-39Ar dating of pseudotachylytes: the effect of clast-hosted extraneous argon in Cenozoic fault-generated friction melts from the West Antarctic <span class="hlt">Rift</span> <span class="hlt">System</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Fault-generated pseudotachylytes are the product of frictional melting during high-velocity slip associated with coseismic faulting. 40Ar-39Ar dating of pseudotachylytes represents a powerful tool to directly determine the age of brittle faulting which is otherwise dated only indirectly. However, the pronounced spatial heterogeneity of most endogenically generated pseudotachylytes, due to the intimate coexistence of unmelted mineral clasts from the source rock, frictional glass and neogenic igneous minerals, often precludes a straightforward interpretation of argon data. This requires careful evaluation of the role of clasts in plaguing the age record of the pseudotachylyte matrix. This study exploits the full potential of the 40Ar-39Ar method, using laser step-heating and laser in situ techniques in conjunction with textural and chemical characterisation at the microscale to disentangle the complexity of the first record of pseudotachylytes generated in the right-lateral fault <span class="hlt">systems</span> which dissect the western shoulder of the West Antarctic <span class="hlt">Rift</span> <span class="hlt">System</span>. Pseudotachylytes occur as fault and injection veins. They exhibit glassy matrices with a potassium feldspar-like composition, and invariably contain, at a millimeter to microscopic scale, unmelted quartz and subordinate feldspars from the source rock. Injection veins characteristically contain much fewer mineral clasts. In situ ultraviolet (UV) laser analyses indicate that quartz from the host rock and from clasts within the fault veins contains significant amounts (~10-50 ppb) of parentless 40Ar, most probably hosted in microscopic to submicroscopic fluid inclusions, associated with high Cl/K ratios. Infrared laser step-heating experiments on fault vein pseudotachylyte matrices yield strongly discordant age spectra with an overall saddle shape characterised by a minimum at ~34 Ma, unrealistically old ages at high temperatures associated with high Cl/K ratios and total gas ages of 41.5-44.3 Ma. Petrographic data and the pronounced compositional similarity between in situ UV laser data on quartz and the high-temperature end member of step-heating analyses suggest that quartz is the main contaminant of the pseudotachylyte age record. In situ laserprobe analyses on pseudotachylyte matrices give concordant ages at ~34 Ma for an injection vein and systematically older ages, clustering at ~40-48 Ma, for fault veins. Although the age cluster fits into the Cenozoic tectonic framework of the region, it is an artefact due to the low spatial resolution of the argon laserprobe compared to the size and spatial distribution of quartz clasts within the pseudotachylyte. The isochron age of 34.11+/-0.96 Ma, derived from in situ data from the injection vein, overlaps with the emplacement age of syn-tectonic dykes from nearby areas and is interpreted to date a single episode of coseismic faulting. Regionally, the age of the studied pseudotachylytes represents the first direct onshore evidence of right-lateral strike-slip fault <span class="hlt">system</span> activity in Victoria Land during the Cenozoic.</p> <div class="credits"> <p class="dwt_author">di Vincenzo, Gianfranco; Rocchi, Sergio; Rossetti, Federico; Storti, Fabrizio</p> <p class="dwt_publisher"></p> <p class="publishDate">2004-07-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">192</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/56494388"> <span id="translatedtitle"><span class="hlt">Rift</span> to Post-<span class="hlt">rift</span> evolution of a</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Low-temperature thermochronology was applied at the Brazilian passive continental margin in order to understand and reconstruct the post-<span class="hlt">rift</span> evolution since the break-up of southwestern Gondwana. Thermochronological data obtained from apatite fission-track analysis of Neoproterozoic metamorphic and Paleozoic to Mesozoic siliciclastic rocks as well as Mesozoic dikes from the Ponta Grossa Arch provided ages between 66.2 (1.3) and 5.9 (0.8) Ma.</p> <div class="credits"> <p class="dwt_author">Ana. O. B. Franco-Magalhaes; Peter C. Hackspacher; Ulrich A. Glasmacher; A. R. Saad</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">193</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/5079211"> <span id="translatedtitle">Discontinuous and diachronous evolution of the Main Ethiopian <span class="hlt">Rift</span>: Implications for development of continental <span class="hlt">rifts</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The Main Ethiopian <span class="hlt">Rift</span> (MER) is commonly considered the archetypal magma-assisted <span class="hlt">rift</span>. Tomographic images of upper-mantle upwellings beneath the <span class="hlt">rift</span>, aligned anisotropy beneath magmatic segments, and pervasive magmatic modification of the crust all indicate the importance of magmatic processes in present-day <span class="hlt">rift</span> evolution. It has been suggested that this magmatic development is responsible for the straight and continuous path the</p> <div class="credits"> <p class="dwt_author">K. Keranen; S. L. Klemperer</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">194</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2008E%26PSL.265...96K"> <span id="translatedtitle">Discontinuous and diachronous evolution of the Main Ethiopian <span class="hlt">Rift</span>: Implications for development of continental <span class="hlt">rifts</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Main Ethiopian <span class="hlt">Rift</span> (MER) is commonly considered the archetypal magma-assisted <span class="hlt">rift</span>. Tomographic images of upper-mantle upwellings beneath the <span class="hlt">rift</span>, aligned anisotropy beneath magmatic segments, and pervasive magmatic modification of the crust all indicate the importance of magmatic processes in present-day <span class="hlt">rift</span> evolution. It has been suggested that this magmatic development is responsible for the straight and continuous path the <span class="hlt">rift</span> cuts across the Ethiopian Plateau. We compile new evidence indicating that the MER is not as continuous and its development not as simple as previously believed. Significant lithospheric heterogeneities are evident in our compilation of recently acquired seismic, gravity, and geologic data. Numerical models of <span class="hlt">rift</span> propagation in such heterogeneous lithosphere show that <span class="hlt">rift</span> propagation may stall at rheological boundaries. We propose that the heterogeneities in the MER caused irregular <span class="hlt">rift</span> propagation, resulting in a distinct discontinuity visible within the <span class="hlt">rift</span> lithosphere. This discontinuity in structure spatially correlates to an apparent discontinuity in the age of extension between the northern MER and the central MER, lending support to our hypothesis. Our interpretation leads to a two-phase model of <span class="hlt">rift</span> propagation in the MER, with initial <span class="hlt">rift</span> development primarily controlled by lithospheric structure and a later phase during which magmatic processes are dominant. During the initial phase, <span class="hlt">rift</span> propagation was irregular and at times stalled or was diverted away from the modern <span class="hlt">rift</span> trend along pre-existing structures. Our model, while acknowledging the importance of magmatic processes in volcanic extensional regions, shows that even in this classic example of magma-assisted <span class="hlt">rifting</span>, inherited lithospheric structure localized initial extension and controlled <span class="hlt">rift</span> propagation. This early phase formed the template for future <span class="hlt">rift</span> development and continental break-up.</p> <div class="credits"> <p class="dwt_author">Keranen, K.; Klemperer, S. L.</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">195</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/14897751"> <span id="translatedtitle">Lithospheric structure of the Rio Grande <span class="hlt">rift</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">A high-resolution, regional passive seismic experiment in the Rio Grande <span class="hlt">rift</span> region of the southwestern United States has produced new images of upper-mantle velocity structure and crust-mantle topography. Synthesizing these results with geochemical and other geophysical evidence reveals highly symmetric lower-crustal and upper-mantle lithosphere extensional deformation, suggesting a pure-shear <span class="hlt">rifting</span> mechanism for the Rio Grande <span class="hlt">rift</span>. Extension in the lower</p> <div class="credits"> <p class="dwt_author">David Wilson; Richard Aster; Michael West; James Ni; Steve Grand; Wei Gao; W. Scott Baldridge; Steve Semken; Paresh Patel</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">196</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40699586"> <span id="translatedtitle">Hydrothermal bitumen generated from sedimentary organic matter of <span class="hlt">rift</span> lakes – Lake Chapala, Citala <span class="hlt">Rift</span>, western Mexico</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Lake Chapala is in the Citala <span class="hlt">Rift</span> of western Mexico, which in association with the Tepic-Zacoalco and Colima <span class="hlt">Rifts</span>, form the well-known neotectonic Jalisco continental triple junction. The <span class="hlt">rifts</span> are characterized by evidence for both paleo- and active hydrothermal activity. At the south shore of the lake, near the Los Gorgos sublacustrine hydrothermal field, there are two tar emanations that</p> <div class="credits"> <p class="dwt_author">Pedro F. Zárate-del Valle; Bernd R. T. Simoneit</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">197</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/54528210"> <span id="translatedtitle">Igneous Intrusion Control on Stress in Continental <span class="hlt">Rift</span> Zones and the Impact on <span class="hlt">Rift</span> Evolution</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Igneous intrusions, both contemporaneous with and pre-dating continental <span class="hlt">rifting</span>, strongly affect stress fields within and adjacent to the <span class="hlt">rift</span> and may control major <span class="hlt">rift</span> processes including future volcanism, segmentation, propagation, and overall evolution. The effect of intrusive bodies on stress in an extensional regime depends on the strength of the emplaced material versus the country rock, the greater the strength</p> <div class="credits"> <p class="dwt_author">E. K. Beutel</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">198</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012DPS....4450508A"> <span id="translatedtitle"><span class="hlt">Final</span> Origin of the Saturn <span class="hlt">System</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">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> <div class="credits"> <p class="dwt_author">Asphaug, Erik; Reufer, A.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-10-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">199</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/1988JGR....93.4759B"> <span id="translatedtitle">Deformational models of <span class="hlt">rifting</span> and folding on Venus</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Features of presumed tectonic origin on Venus are reviewed, and lithospheric strength envelopes are derived based on laboratory measurements of the deformational properties of crustal and subcrustal rocks, extrapolated to conditions appropriate to Venus. Models for <span class="hlt">rifting</span> and folding are developed that use this lithospheric structure and take into account both brittle and ductile yielding as well as finite elastic strength. For both <span class="hlt">rifting</span> and folding, structures with characteristic widths and spacings are predicted whose size depends on the thickness of the lithosphere, density contrast, and elastic properties of the layer. <span class="hlt">Finally</span>, the model predictions are compared with the widths and spacings of observed tectonic features, and it is concluded that they are consistent with a relatively strong mantle layer separated from a thin brittle surface layer by a ductile lower crust. These results allow constraints to be placed on the crustal thickness and thermal gradient on Venus.</p> <div class="credits"> <p class="dwt_author">Banerdt, W. B.; Golombek, M. P.</p> <p class="dwt_publisher"></p> <p class="publishDate">1988-05-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">200</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2005DPS....37.3219G"> <span id="translatedtitle">Elastic Lithosphere Thickness and Heat Flux Estimates from <span class="hlt">Rift</span> Valley Topography: Coracis Fossae, Mars</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Coracis Fossae in the Thaumasia region on Mars are two several hundred kilometer long and ˜50 km wide extensional structures. Their complex morphology, fractured graben floors and segmented border faults, which are arranged in en echelon pattern, suggest that they are Martian analogues to terrestrial <span class="hlt">rift</span> <span class="hlt">systems</span>. At Coracis Fossae's NE segment <span class="hlt">rift</span> flank uplift is most pronounced, the <span class="hlt">rift</span> shoulders having heights of more than 1000 m with respect to the surrounding planes. We model the uplift by fitting a flexed broken plate to the topography data obtained by the Mars Orbiter Laser Altimeter. Thus, the elastic thickness at the time of <span class="hlt">rifting</span> is constrained to 10.3 - 12.5 km. Assuming a diabase composition of the crust, this corresponds to a thermal gradient of 27 - 33 K km-1. Investigating the key surface units associated with the <span class="hlt">rifting</span>, the time of <span class="hlt">rift</span> formation is determined by measuring their crater size-frequency distribution and comparing the results to an impact cratering chronology model. The time of <span class="hlt">rifting</span> is thus constrained to 3.5 - 3.9 Gyr b.p. Given the fault block topography and elastic thickness, the stresses acting on the bounding faults which support the topography may be calculated. We estimate that at the Coracis Fossae the faults need not withstand stresses in excess of 5 MPa, a value comparable to terrestrial faults. We take this weakness as an indication that the faults are or have been in contact with liquid water below the surface.</p> <div class="credits"> <p class="dwt_author">Grott, M.; Hauber, E.; Werner, S. C.; Kronberg, P.; Neukum, G.</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-08-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_9");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a onClick='return showDiv("page_3");' href="#">3</a> <a onClick='return 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id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_10");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a onClick='return showDiv("page_3");' href="#">3</a> <a onClick='return showDiv("page_4");' href="#">4</a> <a onClick='return showDiv("page_5");' href="#">5</a> <a onClick='return showDiv("page_6");' href="#">6</a> <a onClick='return showDiv("page_7");' href="#">7</a> <a onClick='return showDiv("page_8");' href="#">8</a> <a onClick='return showDiv("page_9");' href="#">9</a> <a onClick='return showDiv("page_10");' href="#">10</a> <a style="font-weight: bold;">11</a> <a onClick='return showDiv("page_12");' href="#">12</a> <a onClick='return showDiv("page_13");' href="#">13</a> <a onClick='return showDiv("page_14");' href="#">14</a> <a onClick='return showDiv("page_15");' href="#">15</a> <a onClick='return showDiv("page_16");' href="#">16</a> <a onClick='return showDiv("page_17");' href="#">17</a> <a onClick='return showDiv("page_18");' href="#">18</a> <a onClick='return showDiv("page_19");' href="#">19</a> <a onClick='return showDiv("page_20");' href="#">20</a> <a onClick='return showDiv("page_21");' href="#">21</a> <a onClick='return showDiv("page_22");' href="#">22</a> <a onClick='return showDiv("page_23");' href="#">23</a> <a onClick='return showDiv("page_24");' href="#">24</a> <a onClick='return showDiv("page_25");' href="#">25</a> </span> </span> <a id="NextPageLink" onclick='return showDiv("page_12");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">201</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2008AGUFM.B51D0407C"> <span id="translatedtitle">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> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">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> <div class="credits"> <p class="dwt_author">Cron, B. R.; Crossey, L.; Hall, J.; Takacs-Vesbach, C.; Dahm, K.; Northup, D.; Karlstrom, K.</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">202</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40074504"> <span id="translatedtitle">A stratigraphical-geochemical study on the Chaco Paraná continental <span class="hlt">rift</span> basin—An approach study based on regional sedimentology and drill-hole core analyses, South América</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">This paper is focused on a geologic “regional <span class="hlt">rift</span> basin <span class="hlt">system</span> pattern” and its stratigraphicalgeochemical relationship.\\u000a This is mainly based on the littoral shallow marine sedimentary succession paleogeography and deposits. These successions\\u000a characterize the large extensional intracratonic Chaco Paraná Basin <span class="hlt">rift</span> <span class="hlt">system</span>. The basin is located in South America west\\u000a of the Brazilian Shield. The analyzed <span class="hlt">rift</span> basin <span class="hlt">system</span> evolved</p> <div class="credits"> <p class="dwt_author">Roberto Torra</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">203</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/48923414"> <span id="translatedtitle">Oblique-slip deformation in extensional terrains: A case study of the lakes Tanganyika and Malawi <span class="hlt">Rift</span> Zones</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The East African <span class="hlt">Rift</span> <span class="hlt">system</span> (EAR) is the archetypal continental <span class="hlt">rift</span> and a widely proposed analogue for the early stages of evolution of passive continental margins. The three-dimensional structure of parts of the EAR has been recently elucidated by a multifold seismic (MFS) survey of Lakes Tanganyika and Malawi (Project PROBE). Analysis of fault geometries displayed on the PROBE MFS</p> <div class="credits"> <p class="dwt_author">Deborah L. Scott; Michael A. Etheridge; Bruce R. Rosendahl</p> <p class="dwt_publisher"></p> <p class="publishDate">1992-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">204</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012Tecto..31.4001P"> <span id="translatedtitle">Tectono-stratigraphic signature of multiphased <span class="hlt">rifting</span> on divergent margins (deep-offshore southwest Iberia, North Atlantic)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Regional 2D multichannel seismic, borehole, dredge and outcrop data, together with burial models for strata in southwest Iberia, are used to investigate the tectono-stratigraphic signature of multiphased <span class="hlt">rifting</span> on divergent margins. Our burial model reveals that Mesozoic extension occurred during three main phases, each comprising distinct subsidence pulses separated by short-lived periods of crustal uplift. The importance of the three phases varies across discrete sectors of the margin, each one revealing similar depositional architectures and associated tectonic <span class="hlt">systems</span> tracts: 1) the <span class="hlt">Rift</span> Initiation phase, characterized by incipient subsidence and overall aggradation/progradation over a basal unconformity, 2) the <span class="hlt">Rift</span> Climax phase, which marks maxima of tectonic subsidence and is characterized by retrogradation-progradation, and 3) the Late <span class="hlt">Rift</span> phase, recording the progradational infill of the basin and the effects of eustasy. The <span class="hlt">Rift</span> Initiation <span class="hlt">systems</span> tracts comprise Sinemurian and late Callovian-early Oxfordian strata. Marine units in the Pliensbachian and Late Oxfordian-Kimmeridgian represent the <span class="hlt">Rift</span> Climax phase, a period marked by the development of Maximum Flooding Surfaces. Late <span class="hlt">Rift</span> deposits were identified in the Rhaetian-Hettangian, Toarcian-Bathonian and Kimmeridgian-Berriasian. The results of this work are important to the economic exploration of deep-offshore <span class="hlt">rift</span> basins, as they reveal that sequence stratigraphy can be used to predict sedimentary facies distribution in more distal segments of such basins. Significantly, this work recognizes that multiple tectonic-stratigraphic (<span class="hlt">rift</span>) cycles can occur on deep-offshore <span class="hlt">rift</span> basins, from the onset of <span class="hlt">rift</span>-related extension until continental break-up, a character that contrast to what is known from deep-sea drilling data from the distal margin of Northwest Iberia.</p> <div class="credits"> <p class="dwt_author">Pereira, Ricardo; Alves, Tiago M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-08-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">205</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/6536182"> <span id="translatedtitle">Rio Grande <span class="hlt">rift</span>: problems and perspectives</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">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> <div class="credits"> <p class="dwt_author">Baldridge, W.S.; Olsen, K.H.; Callender, J.F.</p> <p class="dwt_publisher"></p> <p class="publishDate">1984-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">206</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/44252298"> <span id="translatedtitle">Cenozoic <span class="hlt">rift</span> formation in the northern Caribbean</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary"><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</p> <div class="credits"> <p class="dwt_author">Paul Mann; Kevin Burke</p> <p class="dwt_publisher"></p> <p class="publishDate">1984-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">207</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/1997Tectp.278...63M"> <span id="translatedtitle">Two-stage <span class="hlt">rifting</span> in the Kenya <span class="hlt">rift</span>: implications for half-graben models</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Kerio sub-basin in the northern Kenya <span class="hlt">rift</span> is a transitional area between the southern Kenya <span class="hlt">rift</span>, where crustal thickness is 30 km, and the northern Kenya <span class="hlt">rift</span>, where crustal thickness is 20 km. The lack of data on the shallow crustal structure, geometry of <span class="hlt">rift</span>-bounding faults, and <span class="hlt">rift</span> evolution makes it difficult to determine if the crustal thickness variations are due to pre-<span class="hlt">rift</span> structure, or along-axis variations in crustal stretching. We reprocessed reflection seismic data acquired for the National Oil Corporation of Kenya, and integrated results with field and gravity observations to (1) delineate the sub-surface geometry of the Kerio sub-basin, (2) correlate seismic stratigraphic sequences with dated strata exposed along the basin margins, and (3) use new and existing results to propose a two-stage <span class="hlt">rifting</span> model for the central Kenya <span class="hlt">rift</span>. Although a classic half-graben form previously had been inferred from the attitude of uppermost strata, new seismic data show a more complex form in the deeper basin: a narrow full-graben bounded by steep faults. We suggest that the complex basin form and the northwards increase in crustal thinning are caused by the superposition of two or more <span class="hlt">rifting</span> events. The first <span class="hlt">rifting</span> stage may have occurred during Palaeogene time contemporaneous with sedimentation and <span class="hlt">rifting</span> in northwestern Kenya and southern Sudan. The distribution of seismic sequences suggests that a phase of regional thermal subsidence occurred prior to renewed faulting and subsidence at about 12 Ma after the eruption of flood phonolites throughout the central Kenya <span class="hlt">rift</span>. A new border fault developed during the second <span class="hlt">rifting</span> stage, effectively widening the basin. Gravity and seismic data indicate sedimentary and volcanic strata filling the basin are 6 km thick, with up to 4 km deposited during the first <span class="hlt">rifting</span> stage.</p> <div class="credits"> <p class="dwt_author">Mugisha, F.; Ebinger, C. J.; Strecker, M.; Pope, D.</p> <p class="dwt_publisher"></p> <p class="publishDate">1997-09-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">208</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40448226"> <span id="translatedtitle">Quaternary oblique extensional tectonics in the Ethiopian <span class="hlt">Rift</span> (Horn of Africa)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The Ethiopian <span class="hlt">Rift</span> extends in a northeasterly direction, from Southern Ethiopia to the Afar region. It shows a complex fault pattern, characterised by the interplay of a N30°E—N40°E-trending border fault <span class="hlt">system</span> with the Quaternary Wonji Fault Belt, which is constituted by right-stepping en-echelon N?S to N20°E trending faults. The Wonji Fault Belt affects mainly the <span class="hlt">rift</span> floor, but it also</p> <div class="credits"> <p class="dwt_author">Mario Boccaletti; Marco Bonini; Roberto Mazzuoli; Bekele Abebe; Luigi Piccardi; Luigi Tortorici</p> <p class="dwt_publisher"></p> <p class="publishDate">1998-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">209</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/55025154"> <span id="translatedtitle">Shortening deformation of the back-arc <span class="hlt">rift</span> basin in the central northern Honshu, Japan</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The Pacific plate is being subducted beneath northern Honshu, Japan, forms a classical example of trench-arc-back arc <span class="hlt">system</span>. The compressional stress, perpendicular to the northern Honshu arc, has produced the shortening deformation in the Miocene back arc <span class="hlt">rift</span> basins since the Pliocene. Two narrow up-<span class="hlt">rift</span> zones run parallel to the arc: Dewa hills on the west and Ou Backbone range</p> <div class="credits"> <p class="dwt_author">N. Kato; H. Sato</p> <p class="dwt_publisher"></p> <p class="publishDate">2003-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">210</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011E%26PSL.307..461M"> <span id="translatedtitle">Transient <span class="hlt">rifting</span> north of the Galápagos Triple Junction</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Seafloor bathymetry north of the Galápagos microplate in the Eastern Pacific Ocean contains evidence for a sequence of short-lived <span class="hlt">rifts</span> cross-cutting abyssal hills adjacent to the East Pacific Rise. These secondary <span class="hlt">rifts</span> are sub-parallel to the Incipient <span class="hlt">Rift</span> that marks the current triple junction at 2°40'N and are nearly perpendicular to the direction of opening between the Cocos and Nazca plates. Secondary <span class="hlt">rifts</span> likely initiated from the EPR by lithospheric cracking. Eventually, their activity stopped and they were carried away from the triple junction as part of the Cocos plate. We developed and analyzed numerical models of <span class="hlt">rift</span> interaction to understand the evolution of <span class="hlt">rift</span> configuration in this area. By varying the geometry and locations of <span class="hlt">rifts</span>, we constrain the factors that have led to the location and orientation of secondary <span class="hlt">rifts</span> at the northern Galápagos Triple Junction. Interaction between secondary <span class="hlt">rifts</span> and the Cocos-Nazca <span class="hlt">Rift</span> results in ~ 10° clockwise rotation of the secondary <span class="hlt">rift</span> propagation direction, as observed. Furthermore, if a <span class="hlt">rift</span> has become detached from the East Pacific Rise, a zone of reduced tension is present ahead of the <span class="hlt">rift</span> tip, prohibiting its connection to the East Pacific Rise. Two zones of tensile stress enhancement develop along the East Pacific Rise next to the detached <span class="hlt">rift</span> and control where new cracks are likely to form. Although the magnitude of tensile stress enhancement is controlled by the gap between the detached <span class="hlt">rift</span> and the East Pacific Rise, whether the new <span class="hlt">rift</span> forms north or south of the detached <span class="hlt">rift</span> is controlled by position of the Cocos-Nazca <span class="hlt">Rift</span>. Therefore, the sequence of ancient <span class="hlt">rifts</span> found northeast of the current triple junction at 2°40'N represents the natural consequence of <span class="hlt">rift</span> disconnection events and their position records the kinematic history of the gap between the East Pacific Rise and the Cocos-Nazca <span class="hlt">Rift</span>.</p> <div class="credits"> <p class="dwt_author">Mitchell, Garrett A.; Montési, Laurent G. J.; Zhu, Wenlu; Smith, Deborah K.; Schouten, Hans</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-07-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">211</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/6926304"> <span id="translatedtitle">Flexural modeling of the midcontinent <span class="hlt">rift</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">A basement profile obtained from seismic reflection data has been used to constrain a two-dimensional flexural model of basin formation for the Midcontinent <span class="hlt">Rift</span> at a latitude of 45/sup 0/25'N. Model parameters included the thickness of the elastic plate, the basin width, and the maximum basin thickness. Modeling suggests that flexure produced a deep narrow basin along the <span class="hlt">rift</span> axis and that the crust was thinned at the time of basin formation to an elastic thickness of 9.6 km for a plate ruptured by <span class="hlt">rifting</span>, or 5.7 km for an unbroken plate, with corresponding maximum basin thicknesses of 14 km and 16 km respectively. The plate thickness depends most strongly on the basin width and is well constrained by the seismic data, although erosion may have narrowed the basin. The maximum basin thickness is poorly constrained because of the lack of seismic data for depths greater than about 10 km and because the strata at the center of the <span class="hlt">rift</span> have been disturbed by a postrift compressional event which produced the St. Croix horst. Despite uncertainty about the basin thickness, the load required to flex the crust to produce the Midcontinent <span class="hlt">Rift</span> basin is too large to be attributed to the weight of the central flood basalts unless the basin subsided into a fluid less dense than the solidified basalts. On the basis of seismic refraction data and by analogy with other <span class="hlt">rifts</span>, we hypothesize that a magnetic ''<span class="hlt">rift</span> pillow'' intruded in the lower crust. The basaltic pillow subsequently solidified to produce a large, high-velocity region in the lower crust, centered under the <span class="hlt">rift</span> axis, as determined from deep seismic refraction. This crystallization and cooling may be responsible for the ''sag'' phase of <span class="hlt">rift</span> evolution, as evidenced by laterally widespread occurrence of postvolcanic sediments. copyright American Geophysical Union 1988</p> <div class="credits"> <p class="dwt_author">Nyquist, J.E.; Wang, H.F.</p> <p class="dwt_publisher"></p> <p class="publishDate">1988-08-10</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">212</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/55889459"> <span id="translatedtitle">How Is Lower Crust Modified As A Neo-<span class="hlt">Rift</span> Becomes A Paleo-<span class="hlt">Rift</span> and Part Of The Craton?</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The Southern Oklahoma Aulacogen (SOA), at the southern end of Laurentia (present coordinates), if behaving as neo-<span class="hlt">rifts</span>, such as the Rio Grande <span class="hlt">Rift</span>, presumably possessed a <span class="hlt">rift</span> structure in the Cambrian with a continental thickness of about 28km. Seismic data, though sparse, suggest a present thickness of the SOA is about 45km, indistinguishable from adjacent <span class="hlt">rifted</span> Proterozoic crust. By what</p> <div class="credits"> <p class="dwt_author">M. C. Gilbert</p> <p class="dwt_publisher"></p> <p class="publishDate">2004-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">213</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013GGG....14.2575S"> <span id="translatedtitle">Quantification and restoration of extensional deformation along the Western Iberia and Newfoundland <span class="hlt">rifted</span> margins</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Many recent papers describe the structure of the Iberia and Newfoundland <span class="hlt">rifted</span> margins; however, none of them propose kinematic restorations of the complete <span class="hlt">rift</span> <span class="hlt">system</span> to quantify the amount of extension necessary to exhume mantle and initiate seafloor spreading. In our study, we use two pairs of cross sections considered as conjugate lines: one across the Galicia Bank-Flemish Cap and the other across the Southern Iberia Abyssal Plain-Flemish Pass. Both transects have been imaged by reflection- and refraction-seismic methods and have been drilled during Ocean Drilling Program Legs 103, 149, 173, and 210. Drilling penetrated parts of the <span class="hlt">rift</span> stratigraphy and the underlying basement. The cross sections can therefore be considered as the best-documented conjugate transects across present-day hyperextended, magma-poor <span class="hlt">rifted</span> margins. The aim of this paper is threefold: (1) provide a detailed description of the crustal architecture of the two conjugate sections, (2) define the extensional structures and their ages, and (3) quantify the amount of strain and strain rate accommodated along these lines. This paper proposes a quantitative description of extension along the Iberia-Newfoundland <span class="hlt">rift</span> <span class="hlt">system</span> and discusses the limitations and problems in quantifying extensional deformation along hyperextended <span class="hlt">rifted</span> margins.</p> <div class="credits"> <p class="dwt_author">Sutra, Emilie; Manatschal, Gianreto; Mohn, Geoffroy; Unternehr, Patrick</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-08-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">214</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/14819896"> <span id="translatedtitle">Age of volcanism and <span class="hlt">rifting</span> in southwestern Ethiopia</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">It has been suggested that volcanism in the Ethiopian region of the Afro-Arabian <span class="hlt">Rift</span> <span class="hlt">System</span> has migrated with time, both laterally towards the present axial zone1-3 and longitudinally southwards from the Red Sea4,5. Field data and K-Ar isotopic ages from southwestern Ethiopia, summarised below, indicate that volcanism in this area began earlier than previously suspected, and that Quaternary volcanism was</p> <div class="credits"> <p class="dwt_author">A. Davidson; D. C. Rex</p> <p class="dwt_publisher"></p> <p class="publishDate">1980-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">215</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011AGUFM.T42A..02B"> <span id="translatedtitle">Tectonic heritage and intra-crustal decoupling: consequences for post-orogenic <span class="hlt">rift</span> basin dynamics</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">It is generally accepted that styles of continental <span class="hlt">rifting</span> are conditioned by the integrated strength of the lithosphere. For example, strong plates would extend in narrow <span class="hlt">rifting</span> mode, while weak lithospheres would undergo stretching in wide <span class="hlt">rifting</span> mode. In case of post-orogenic extensional basins this interpretation might be insufficient because it is based on the assumption of "standard" rheological structure of the continental crust, in which creep activation temperature increases with depth, the yield strength profile is characterized by smooth vertical variations , and more basic, denser layers underlay less basic (quartz-rich) low density layers. Yet, the orogenic crusts are largely formed by nappe stacking where strong dense, former lower crustal units slide over less dense weaker former uppers crustal units, resulting in inversed density-rheological sequences. Over-thickened continental crusts are also prone to metamorphic phase changes leading to additional variations in density and rheological properties. As result, unusual, "inversed" rheological structures may form characterized by sharp mechanical contrasts between the lithological layers and by presence of stronger heavy units on top of weaker low density units. To investigate the consequences of such structural heritage and of the associated structural weakening, we implement thermo-mechanical viscous-elastic-plastic numerical models of post-orogenic <span class="hlt">rifting</span>. The experiments show that the inverted post-orogenic structures favor rapid development of mechanical and gravitational instabilities leading to variety of basin morphologies. In particular, wide <span class="hlt">rifts</span> can form in quite strong lithospheres and then "switch" to narrow <span class="hlt">rifting</span> mode. In other cases several <span class="hlt">rift</span> basins develop quasi simultaneously, or low-angle faults and crustal detachments form without necessity of specific rheological mechanisms. The presence of rheological decoupling zones between different crustal and mantle layers is also of primary importance because it results in overall drop of the flexural strength of the <span class="hlt">system</span> and leads to important horizontal flow of the ductile material. In this case crustal necking occurs at different levels so that necking levels switch from one depth to another resulting in step-like variations of <span class="hlt">rifting</span> style and in acceleration/deceleration of subsidence during the active phase of <span class="hlt">rifting</span>. During the post-<span class="hlt">rifting</span> phase, the initially decoupled rheological layers may "stick" together resulting in step-like strengthening of the lithosphere and deceleration of subsidence. Hence, the entire <span class="hlt">rift</span> <span class="hlt">system</span> may exhibit polyphase subsidence history, yet conditioned by the evolution of the internal structure and not by variation of external factors such as far-field forces or mantle dynamics.</p> <div class="credits"> <p class="dwt_author">Burov, E. B.; Huet, B.; Le Pourhiet, L.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">216</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ntis.gov/search/product.aspx?ABBR=BNL24099"> <span id="translatedtitle">Hydrogen Supplementation <span class="hlt">System</span> Evaluation Study. <span class="hlt">Final</span> Report.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ntis.gov/search/index.aspx">National Technical Information Service (NTIS)</a></p> <p class="result-summary">An economic assessment was made of producing and utilizing electrolytic H sub 2 based on applications by typical electric/gas utility <span class="hlt">systems</span>. The four <span class="hlt">systems</span> selected for evaluation are Mid-Atlantic (combination electric/gas <span class="hlt">system</span>, summer electric peak...</p> <div class="credits"> <p class="dwt_author">W. S. Ku D. C. Nielsen J. Zemkoski D. L. Leich P. Yatcko</p> <p class="dwt_publisher"></p> <p class="publishDate">1977-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">217</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/60015047"> <span id="translatedtitle">Pneumatic transport <span class="hlt">system</span> development. <span class="hlt">Final</span> report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Data on solids transfer rates, <span class="hlt">system</span> reliability, residual material in the <span class="hlt">system</span>, degree of homogeneity before and after transport of blended nuclear fuel powders, erosion in the elbows, and materials of construction were generated to provide confirmation of the design criteria necessary for the implementation of a dilute phase pneumatic transport <span class="hlt">system</span> in a commercial mixed oxide fuel facility. From</p> <div class="credits"> <p class="dwt_author">E. E. Smeltzer; D. A. Eckhardt; W. C. Yang; M. C. Skriba</p> <p class="dwt_publisher"></p> <p class="publishDate">1979-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">218</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/6453089"> <span id="translatedtitle">Integrated particle sizing <span class="hlt">system</span>. Draft <span class="hlt">final</span> report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The new Integrated Particle Sizing <span class="hlt">system</span> (IPSS Model 100) has been constructed with substantial improvements in the optical, mechanical, and electronic designs. The new <span class="hlt">system</span> is simple to operate and remains stable over a long period of operation. Results of a continuous 100-hour monitoring of particulate from the combustion of pulverized coal using this <span class="hlt">system</span> is presented.</p> <div class="credits"> <p class="dwt_author">Poon, C.C.; Houser, M.J.; Bachalo, W.D.</p> <p class="dwt_publisher"></p> <p class="publishDate">1981-04-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">219</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://files.eric.ed.gov/fulltext/ED506081.pdf"> <span id="translatedtitle"><span class="hlt">Final</span> Paper DAT Cognitive Art Therapy <span class="hlt">System</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p class="result-summary">|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> <div class="credits"> <p class="dwt_author">Jacobson, Eric</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">220</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2005JGRE..110.7003H"> <span id="translatedtitle">The large Thaumasia graben on Mars: Is it a <span class="hlt">rift</span>?</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">We investigate the morphology and topography of one of the largest fault-bounded tectonic structures on Mars, a complex, approximately N-S trending <span class="hlt">system</span> of troughs and scarps at the western border of the Thaumasia plateau in the Claritas region (hereinafter referred to as ``Thaumasia graben,'' or TG). It is located between 15°S and 38°S latitude and at ~255°E longitude. No detailed investigation of its morphotectonic setting has been performed yet. The region is a complexly fractured area with a number of different fault sets, including simple and complex graben. The TG extends over more than 1000 km along its trend, averaging 100 km in width and 1.6 km in depth. Crustal extension is accommodated by the formation of a <span class="hlt">system</span> of asymmetric graben, or halfgraben. On the basis of fault orientation and trough depth, the TG can be subdivided in a north-south direction into three segments. Except for the northernmost segment, the predominant master fault <span class="hlt">system</span> is located along the eastern flank of the TG, highlighting the overall asymmetric architecture. Fault length segments vary from 50 to 90 km with observable displacements of 1.3-2.2 km. Crustal extension, inferred from gridded MOLA topography across scarp offsets, varies along trend between 0.5 km and ~4 km, assuming a fault dip of 60°. This is relatively moderate extension if compared to terrestrial continental <span class="hlt">rifts</span>, but consistent with extension measured across the Tempe <span class="hlt">Rift</span> on Mars. We find that the Thaumasia graben displays some characteristics which are common to terrestrial continental <span class="hlt">rifts</span>, whereas other properties are distinctively not <span class="hlt">rift</span>-like.</p> <div class="credits"> <p class="dwt_author">Hauber, E.; Kronberg, P.</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-07-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_10");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" 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onClick='return showDiv("page_6");' href="#">6</a> <a onClick='return showDiv("page_7");' href="#">7</a> <a onClick='return showDiv("page_8");' href="#">8</a> <a onClick='return showDiv("page_9");' href="#">9</a> <a onClick='return showDiv("page_10");' href="#">10</a> <a onClick='return showDiv("page_11");' href="#">11</a> <a style="font-weight: bold;">12</a> <a onClick='return showDiv("page_13");' href="#">13</a> <a onClick='return showDiv("page_14");' href="#">14</a> <a onClick='return showDiv("page_15");' href="#">15</a> <a onClick='return showDiv("page_16");' href="#">16</a> <a onClick='return showDiv("page_17");' href="#">17</a> <a onClick='return showDiv("page_18");' href="#">18</a> <a onClick='return showDiv("page_19");' href="#">19</a> <a onClick='return showDiv("page_20");' href="#">20</a> <a onClick='return showDiv("page_21");' href="#">21</a> <a onClick='return showDiv("page_22");' href="#">22</a> <a onClick='return showDiv("page_23");' href="#">23</a> <a onClick='return showDiv("page_24");' href="#">24</a> <a onClick='return showDiv("page_25");' href="#">25</a> </span> </span> <a id="NextPageLink" onclick='return showDiv("page_13");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">221</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/841361"> <span id="translatedtitle">Manzanita Hybrid Power <span class="hlt">system</span> Project <span class="hlt">Final</span> Report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">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> <div class="credits"> <p class="dwt_author">Trisha Frank</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-03-31</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">222</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/10178298"> <span id="translatedtitle">Statistical mechanics of polymer <span class="hlt">systems</span>. <span class="hlt">Final</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Work on computer simulation of polymer dynamics and the statistical mechanics of quenched <span class="hlt">systems</span> carried out over seven years with the support of this grant is reviewed. The computer simulation work has focused on elucidation the roles of the excluded volume and the nearest-neighbor attractive interactions in the dynamics of polymers. To study quenched <span class="hlt">systems</span> we have applied the formalism suggested long ago by Mazo to two model <span class="hlt">systems</span> and found qualitative agreement with the properties of real glasses.</p> <div class="credits"> <p class="dwt_author">Kovac, J.</p> <p class="dwt_publisher"></p> <p class="publishDate">1993-06-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">223</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/6348320"> <span id="translatedtitle">Adaptive distribution <span class="hlt">system</span> protection: <span class="hlt">Final</span> report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">This report presents concepts, functions, and organizations of adaptive distribution <span class="hlt">system</span> protection (ADSP) schemes. ADSP constantly monitors real time data, update relay characteristics and upper and lower bounds of control functions when required, and analyzes them to provide faster and more sensitive protection of all distribution <span class="hlt">system</span> components and optimized control of loads, capacitors and reclosing sequence of circuit breakers and reclosers. Three proposed ADSP <span class="hlt">systems</span>, Computer Overcurrent Relaying (COR) <span class="hlt">System</span>, Directional Comparison Relaying (DCR) <span class="hlt">System</span> and Differential Protective Coordination <span class="hlt">System</span>, are discussed in detail. Evaluation of these three <span class="hlt">systems</span> using technical, non-technical and economic parameters has led to the selection of the COR <span class="hlt">system</span> as the most promising ADSP scheme for the following reasons: (1) it is simple to implement, (2) it uses the same protection philosophy and components currently being used by the electric utility industry and (3) it has a high-benefit-to-cost ratio. This report outlines strategies of integrating ADSP schemes into existing electric utility distribution <span class="hlt">systems</span>. 21 refs., 19 figs., 6 tabs.</p> <div class="credits"> <p class="dwt_author">Shan, K.R.</p> <p class="dwt_publisher"></p> <p class="publishDate">1987-06-15</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">224</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3367374"> <span id="translatedtitle"><span class="hlt">Rift</span> Valley Fever in Small Ruminants, Senegal, 2003</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">During the 2003 rainy season, the clinical and serologic incidence of <span class="hlt">Rift</span> Valley fever was assessed in small ruminant herds living around temporary ponds located in the semi-arid region of the Ferlo, Senegal. No outbreak was detected by the surveillance <span class="hlt">system</span>. Serologic incidence was estimated at 2.9% (95% confidence interval 1.0–8.7) and occurred in 5 of 7 ponds with large variations in the observed incidence rate (0%–20.3%). The location of ponds in the Ferlo Valley and small ponds were correlated with higher serologic incidence (p = 0.0005 and p = 0.005, respectively). <span class="hlt">Rift</span> Valley fever surveillance should be improved to allow early detection of virus activity. Ruminant vaccination programs should be prepared to confront the foreseeable higher risks for future epidemics of this disease.</p> <div class="credits"> <p class="dwt_author">Lancelot, Renaud; Thiongane, Yaya; Sall, Baba; Diaite, Amadou; Mondet, Bernard</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">225</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ntis.gov/search/product.aspx?ABBR=PB280633"> <span id="translatedtitle">Hospital Management <span class="hlt">Systems</span> Demonstration; <span class="hlt">Final</span> Report and Executive Summary.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ntis.gov/search/index.aspx">National Technical Information Service (NTIS)</a></p> <p class="result-summary">The documentation of this project consists of the <span class="hlt">final</span> report, a magnetic tape and other appendices through S. The tape contains the computer programs for The Admissions Scheduling and Control <span class="hlt">System</span>: A Comprehensive Hospital Admissions Modeling and Simu...</p> <div class="credits"> <p class="dwt_author">J. R. Griffith W. M. Hancock</p> <p class="dwt_publisher"></p> <p class="publishDate">1977-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">226</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://pubs.er.usgs.gov/publication/70011581"> <span id="translatedtitle">Accumulation of fossil fuels and metallic minerals in active and ancient <span class="hlt">rift</span> lakes</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p class="result-summary">A study of active and ancient <span class="hlt">rift</span> <span class="hlt">systems</span> around the world suggests that accumulations of fossil fuels and metallic minerals are related to the interactions of processes that form <span class="hlt">rift</span> valleys with those that take place in and around <span class="hlt">rift</span> lakes. The deposition of the precursors of petroleum, gas, oil shale, coal, phosphate, barite, Cu-Pb-Zn sulfides, and uranium begins with erosion of uplifted areas, and the consequent input of abundant nutrients and solute loads into swamps and tectonic lakes. Hot springs and volcanism add other nutrients and solutes. The resulting high biological productivity creates oxidized/reduced interfaces, and anoxic and H2S-rich bottom waters which preserves metal-bearing organic tissues and horizons. In the depositional phases, the fine-grained lake deposits are in contact with coarse-grained beach, delta, river, talus, and alluvial fan deposits. Earthquake-induced turbidites also are common coarse-grained deposits of <span class="hlt">rift</span> lakes. Postdepositional processes in <span class="hlt">rifts</span> include high heat flow and a resulting concentration of the organic and metallic components that were dispersed throughout the lakebeds. Postdepositional faulting brings organic- and metal-rich sourcebeds in contact with coarse-grained host and reservoir rocks. A suite of potentially economic deposits is therefore a characteristic of <span class="hlt">rift</span> valleys. ?? 1983.</p> <div class="credits"> <p class="dwt_author">Robbins, E. I.</p> <p class="dwt_publisher"></p> <p class="publishDate">1983-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">227</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ntis.gov/search/product.aspx?ABBR=N9214064"> <span id="translatedtitle">Turbine Engine Diagnostics <span class="hlt">System</span> Study (<span class="hlt">Final</span> Report).</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ntis.gov/search/index.aspx">National Technical Information Service (NTIS)</a></p> <p class="result-summary">The results of a <span class="hlt">system</span> study for the Turbine Engine Diagnostics (TED) program are presented. This research project was initiated to develop a method of approach and prototype design for a <span class="hlt">system</span> capable of predicting the failure of rotating parts in turb...</p> <div class="credits"> <p class="dwt_author">B. K. Mcquiston R. L. Dehoff</p> <p class="dwt_publisher"></p> <p class="publishDate">1991-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">228</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/6010006"> <span id="translatedtitle">Fuel <span class="hlt">system</span> standard test procedure. <span class="hlt">Final</span> report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The purpose of this test procedure is to specify a method that is acceptable to the United States Coast Guard and the equipment to be used in determining whether or not a particular fuel <span class="hlt">system</span> component is in compliance with the Gasoline Fuel <span class="hlt">System</span> Standard in Subpart J of Part 183 of Title 33, Code of Federal Regulations.</p> <div class="credits"> <p class="dwt_author">Not Available</p> <p class="dwt_publisher"></p> <p class="publishDate">1978-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">229</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2003AGUFM.S52J..07M"> <span id="translatedtitle">Analysis of the Junction of the East African <span class="hlt">Rift</span> and the Cretaceous-Paleogene <span class="hlt">Rifts</span> in Northern Kenya and Southern Ethiopia</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The East African <span class="hlt">rift</span> (EAR) is a Tertiary-Miocene <span class="hlt">system</span> that extends from the Middle East, through East Africa, to Mozambique in southern Africa. Much of the present information is from the Ethiopian and Kenyan parts of the <span class="hlt">rift</span>. Several characteristics of the EAR such as <span class="hlt">rift</span>-related volcanism, faulting and topographic relief being exposed make it attractive for studying continental <span class="hlt">rift</span> processes. Structural complexities reflected in the geometries of grabens and half-grabens, the existence of transverse fault zones and accommodation zones, and the influence of pre-existing geologic structures have been documented. In particular, the EAR traverses the Anza graben and related structures near the Kenya/Ethiopian border. The Anza graben is one in a series of Cretaceous-Paleogene failed <span class="hlt">rifts</span> that trend across Central Africa from Nigeria through Chad to Sudan and Kenya with an overall northwest-southeast trend. In spite of a number of recent studies, we do not understand the interaction of these two <span class="hlt">rift</span> <span class="hlt">systems</span>. In both Ethiopia and Kenya, the <span class="hlt">rift</span> segments share some broad similarities in timing and are related in a geographic sense. For example, volcanism appears to have generally preceded or in some cases have been contemporaneous with major <span class="hlt">rift</span> faulting. Although, these segments are distinct entities, each with its own tectonic and magmatic evolution, and they do connect in the region crossed by the Anza graben and related structures. In our present study, we are using a combination of recently collected seismic, gravity and remote sensing data to increase our understanding of these two segments of the EAR. We hope that by analysing the satellite data, the variety and differences in the volume of magmatic products extruded along in southern Ethiopia and northern Kenya will be identified. The geometry of structures (in particular, those causing the gravity axial high) will be modelled to study the impact of the older Anza graben structural trends with the younger EAR. For example there is significant crustal thinning in the Lake Turkana area of the northern Kenya segment of the EAR <span class="hlt">system</span>. In regard to the recent EAGLE experiment in Ethiopia, we are ivestigating if the transition from relatively thick crust (~40 km) to thinned, <span class="hlt">rifted</span> crust is as abrupt in Ethiopia as it is in Kenya.</p> <div class="credits"> <p class="dwt_author">Mariita, N. O.; Tadesse, K.; Keller, G. R.</p> <p class="dwt_publisher"></p> <p class="publishDate">2003-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">230</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013EGUGA..15.8882D"> <span id="translatedtitle">Faulting Mode Characterization using fault attributes : Example of a nascent oceanic <span class="hlt">rift</span> the Manda-Hararo <span class="hlt">rift</span> in Afar (Ethiopia)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Manda-Hararo <span class="hlt">rift</span> segment, located in the Afar depression, underwent a major dyke injection of 65 km long in September 2005, that initiated a <span class="hlt">rifting</span> episode. From June 2006 to May 2010, 13 other successive dykes were intruded and monitored using InSAR and seismic surveys. Aside from its recent activity, the Manda-Hararo <span class="hlt">rift</span> architecture shows some particularities which distinguish the segment North of the central magma chamber from the rest of the <span class="hlt">rift</span>. This Northern segment shows a change of strike of the <span class="hlt">rift</span> axis and of the overlying faults, as well as a marked asymmetry featured by high no-conjugated west-dipping scarps. These observations led to wonder how the Northern part of this <span class="hlt">rift</span> has been integrated into the long-term evolution of the whole <span class="hlt">rift</span>, and whether its deformation mode and fault growth processes might be influenced by the Dabbahu volcano. To address such questions, we focus our analysis on the scaling laws applied to the fault attributes such as fault length, fault scarps or spacing between adjacent faults. This study is based on a fault mapping which was done using optical images (SPOT and, QUICKBIRD images) together with SAR interferograms and coherence images. This map is divided into three regions to isolate the different sources of deformation : the Northern segment close to the Dabbahu volcano, the central one where the main magma reservoir is located and dyke intrusions occurred, and <span class="hlt">finally</span> the southernmost one coinciding with the segment end. A first stage in determining the scaling law, and consequently the growth mode, consists in characterizing the displacement (Dmax) versus length (L) relationship. With our whole dataset and the different groups of segments defined previously, we observe a scattering suggesting no clear evidence for a linear trend associated with self-similar processes. A possible explanation for such observation in addition to the sampling issue would be a distributed mode of deformation (Soliva et al. 2008). Next, for each of these three regions, we determine the distribution law and discuss them in terms of fault growth processes and the possible role of the fragile thickness as a limiting factor. The center and southern regions tend to a gamma law (Davy 1993), unlike the Northern part where an exponential law seems to be more appropriate. Such observation in the Northern part of the <span class="hlt">rift</span> mean that faulting would be distributed and scale dependent, when the central and southern parts would be characterized by a faulting mode closer from the transition localized-distributed. The analysis of scaling laws applied to fault attributes is also discussed in terms of inward-outward dipping faults and compared to the oceanic ridge models (Carbotte et al. 1990). These observations suggest a similar and more advanced stage of evolution for the Central and Southern part of the segment, unlike the Northern segment, which shows a less localized deformation. Indeed, the preferential zone of intrusion of the Northern segment seems to be able to laterally jump over time, as illustrated by the unexpected path taken by the September 2005 intrusion.</p> <div class="credits"> <p class="dwt_author">Dumont, Stéphanie; Socquet, Anne; Doubre, Cécile; Grandin, Raphaël; Klinger, Yann; Medynski, Sarah; Jacques, Eric</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-04-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">231</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/663257"> <span id="translatedtitle">Proximity sensor <span class="hlt">system</span> development. CRADA <span class="hlt">final</span> report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">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> <div class="credits"> <p class="dwt_author">Haley, D.C. [Oak Ridge National Lab., TN (United States); Pigoski, T.M. [Merrit Systems, Inc. (United States)</p> <p class="dwt_publisher"></p> <p class="publishDate">1998-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">232</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ntis.gov/search/product.aspx?ABBR=DE83902305"> <span id="translatedtitle">Railroad Electrification on Utility <span class="hlt">Systems</span>. <span class="hlt">Final</span> Report.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ntis.gov/search/index.aspx">National Technical Information Service (NTIS)</a></p> <p class="result-summary">A nine-month project was undertaken on the subject of the impact of railroad electrification on utility <span class="hlt">systems</span>. The objectives of this study were achieved by a review of the literature, discussions with railroads and electric utilities with electrificati...</p> <div class="credits"> <p class="dwt_author">J. J. Burke J. W. Feltes</p> <p class="dwt_publisher"></p> <p class="publishDate">1983-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">233</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ntis.gov/search/product.aspx?ABBR=PB97188361"> <span id="translatedtitle">Environmental Management <span class="hlt">System</span> Demonstration Project. <span class="hlt">Final</span> Report.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ntis.gov/search/index.aspx">National Technical Information Service (NTIS)</a></p> <p class="result-summary">This report outlines the activities of the Environmental Management <span class="hlt">System</span> (EMS) Demonstration Project, provides an analysis of how the project participants progressed in implementing the ISO 14001 Standard, discusses EMS implementation issues, incentives...</p> <div class="credits"> <p class="dwt_author">C. P. Diamond</p> <p class="dwt_publisher"></p> <p class="publishDate">1996-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">234</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ntis.gov/search/product.aspx?ABBR=DE87013406"> <span id="translatedtitle">Adaptive Distribution <span class="hlt">System</span> Protection: <span class="hlt">Final</span> Report.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ntis.gov/search/index.aspx">National Technical Information Service (NTIS)</a></p> <p class="result-summary">This report presents concepts, functions, and organizations of adaptive distribution <span class="hlt">system</span> protection (ADSP) schemes. ADSP constantly monitors real time data, update relay characteristics and upper and lower bounds of control functions when required, and...</p> <div class="credits"> <p class="dwt_author">K. R. Shan</p> <p class="dwt_publisher"></p> <p class="publishDate">1987-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">235</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ntis.gov/search/product.aspx?ABBR=PB2013109609"> <span id="translatedtitle">Advanced Restraint <span class="hlt">Systems</span> (ARS) <span class="hlt">Final</span> Report: Appendices.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ntis.gov/search/index.aspx">National Technical Information Service (NTIS)</a></p> <p class="result-summary">This report presents a summary of the work performed during the Advanced Restraint <span class="hlt">Systems</span> (ARS) project. The primary objective of this effort was to evaluate the potential benefit of using pre-crash information associated with two unique crash configurat...</p> <div class="credits"> <p class="dwt_author">M. Cuddihy M. P. Weerappuli M. S. Huber S. Cassatta</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">236</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ntis.gov/search/product.aspx?ABBR=PB2013109608"> <span id="translatedtitle">Advanced Restraint <span class="hlt">Systems</span> (ARS) <span class="hlt">Final</span> Report.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ntis.gov/search/index.aspx">National Technical Information Service (NTIS)</a></p> <p class="result-summary">This report presents a summary of the work performed during the Advanced Restraint <span class="hlt">Systems</span> (ARS) project. The primary objective of this effort was to evaluate the potential benefit of using pre-crash information associated with two unique crash configurat...</p> <div class="credits"> <p class="dwt_author">M. Cuddihy M. Struck M. P. Weerappuli M. S. Huber S. Cassatta</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">237</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.geolor.com/East_African_Rift_Valley_geolor.htm"> <span id="translatedtitle">East African <span class="hlt">Rift</span> Valley Links for Learning</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://nsdl.org/nsdl_dds/services/ddsws1-1/service_explorer.jsp">NSDL National Science Digital Library</a></p> <p class="result-summary">This web page contains links to a collection of resources devoted to the East African Valley <span class="hlt">Rift</span>, with emphasis on environmental issues and concerns. It lists web addresses by subtopics, in outline form, with a short description to assist the viewer in searching for information. Topics include The <span class="hlt">Rift</span> Valley, Stromboli online, African volcanoes, the Alid page, paleontology, and many more. The creator of this collection has checked uRLs provided for content and guarantees them to be quality web pages.</p> <div class="credits"> <p class="dwt_author">Moyra/mysticpc; Geolor.com</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">238</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/19908294"> <span id="translatedtitle">The Shear along the Dead Sea <span class="hlt">Rift</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Recent surface and subsurface geological investigations in Israel and Jordan provide new data for the re-examination of Dubertret's (1932) hypothesis of the left-hand shear along the Dead Sea <span class="hlt">rift</span>. It is found that while none of the pre-Tertiary sedimentary or igneous rock units extend right across the <span class="hlt">rift</span>, all of them resume a reasonable palaeographical configuration once the east side</p> <div class="credits"> <p class="dwt_author">R. Freund; Z. Garfunkel; I. Zak; M. Goldberg; T. Weissbrod; B. Derin; F. Bender; F. E. Wellings; R. W. Girdler</p> <p class="dwt_publisher"></p> <p class="publishDate">1970-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">239</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/972164"> <span id="translatedtitle">Analysis of Hybrid Hydrogen <span class="hlt">Systems</span>: <span class="hlt">Final</span> Report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">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> <div class="credits"> <p class="dwt_author">Dean, J.; Braun, R.; Munoz, D.; Penev, M.; Kinchin, C.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">240</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/6364857"> <span id="translatedtitle"><span class="hlt">Final</span> report on the FMIT Control <span class="hlt">System</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The computer control <span class="hlt">system</span> for the Fusion Materials Irradiation Test Facility (FMIT) prototype accelerator was designed using distributed intelligence driven by a distributed database. The <span class="hlt">system</span> consists of two minicomputers in the central control room and four microcomputers residing in CAMAC crates located near appropriate subsystems of the accelerator. The <span class="hlt">system</span> uses single vendor hardware as much as practical in an attempt to minimize the maintenance problems. Local control consoles are an integral part of each node computer to provide subsystem check-out. The main console is located in the central control room and permits one-point operation of the complete control <span class="hlt">system</span>. Automatic surveillance is provided for each data channel by the node computer with out-of-bounds alarms sent to the main console. Report by exception is used for data logging. This control <span class="hlt">system</span> has been operational for two years. The computers are too heavily loaded and the operator response is slower than desired. A <span class="hlt">system</span> upgrade to a faster local-area network has been undertaken and is scheduled to be operational by conference time.</p> <div class="credits"> <p class="dwt_author">Johnson, J.A.</p> <p class="dwt_publisher"></p> <p class="publishDate">1985-01-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_11");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a 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showDiv("page_14");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">241</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/10141858"> <span id="translatedtitle">National Geoscience Data Repository <span class="hlt">System</span>. <span class="hlt">Final</span> report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">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> <div class="credits"> <p class="dwt_author">Schiffries, C.M.; Milling, M.E.</p> <p class="dwt_publisher"></p> <p class="publishDate">1994-03-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">242</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/5005602"> <span id="translatedtitle">The ultra pure water <span class="hlt">system</span>: <span class="hlt">Final</span> report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The design, building and the testing of an Ultra Pure Water Generation <span class="hlt">System</span> that was funded by the Department of Energy (DOE) after first being evaluated by the National Bureau of Standards is covered. This <span class="hlt">system</span> will accept water that is highly polluted with both suspended and dissolved solids. The purification and sterilization is performed in stages. As the water is pumped in, it is first forced through a set of three filters. These filters collect 99% of the particles. The water is then sent through the ion-exchange section which extracts 99.9% of the dissolved solids. The water is then sent through a mixed ion-exchange column and into the the last micro filter. It then is sent to a two gallon holding tank. While in the tank the pure water is polished with ozone gas. The flow through the complete purification <span class="hlt">system</span> is 2 gallons per minute, therefore, its exposure time to ozone in this holdup tank is about 5 minutes. During the time any oxidizable matter, bacteria or viruses left will be destroyed. An important cycle of this unit is the back flush <span class="hlt">system</span>. After each use of the water purification <span class="hlt">system</span>, the unit reverses the flow of water through the larger particle filters.</p> <div class="credits"> <p class="dwt_author">Karlson, E.L.</p> <p class="dwt_publisher"></p> <p class="publishDate">1988-03-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">243</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/207362"> <span id="translatedtitle">Sequencing Information Management <span class="hlt">System</span> (SIMS). <span class="hlt">Final</span> report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">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> <div class="credits"> <p class="dwt_author">Fields, C.</p> <p class="dwt_publisher"></p> <p class="publishDate">1996-02-15</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">244</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/918761"> <span id="translatedtitle">Autonomous microexplosives subsurface tracing <span class="hlt">system</span> <span class="hlt">final</span> report.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">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> <div class="credits"> <p class="dwt_author">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 class="dwt_publisher"></p> <p class="publishDate">2004-04-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">245</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/6063197"> <span id="translatedtitle">Wobbling tube desalination <span class="hlt">system</span>. <span class="hlt">Final</span> technical report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">A single tube vapor compression wobbling tube evaporator (WTE) was developed to establish a heat transfer coefficient about 80% better than that of a vertical tube evaporator. The present grant was intended to complete the objective of the twelve tube <span class="hlt">system</span>. Accomplishments reported include: performance improvement with the single tube testers; design, construction, and preliminary testing of the 64-tube WTE; set up of the periphery equipment; and <span class="hlt">system</span> analysis and study, including the implication for the heat transfer coefficient. Copies of two patents covering the distillation apparatus are appended. (LEW)</p> <div class="credits"> <p class="dwt_author">Li, Y.T.</p> <p class="dwt_publisher"></p> <p class="publishDate">1984-07-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">246</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/60254946"> <span id="translatedtitle">Improved windpower generating <span class="hlt">system</span>. <span class="hlt">Final</span> report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The following report describes a research and development program to investigate an improved windpower generating <span class="hlt">system</span>. The improved rotor design combines the high starting torque of multi-blade horizontal-axis rotors with the high efficiency of ''propeller'' type rotors. The resulting ''compound'' rotor is believed to have significant advantages over more conventional rotors, particularly for pumping operations. The R and D program</p> <div class="credits"> <p class="dwt_author">K. Bergey; J. Frazier; K. Craig; P. Veragen</p> <p class="dwt_publisher"></p> <p class="publishDate">1984-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">247</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/60430561"> <span id="translatedtitle">MIST (multiloop integral <span class="hlt">system</span> test) <span class="hlt">final</span> report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The multiloop integral <span class="hlt">system</span> test (MIST) facility is part of a multiphase program started in 1983 to address small-break loss-of- coolant accidents (SBLOCAs) specific to Babcock Wilcox (B W) designed plants. MIST is sponsored by the US Nuclear Regulatory Commission, the B W Owners Group, the Electric Power Research Institute, and B W. The unique features of the B W</p> <div class="credits"> <p class="dwt_author">J. A. Klingenfus; M. V. Parece</p> <p class="dwt_publisher"></p> <p class="publishDate">1990-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">248</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/61219174"> <span id="translatedtitle">Multiloop Integral <span class="hlt">System</span> Test (MIST): <span class="hlt">Final</span> report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The multiloop integral <span class="hlt">system</span> test (MIST) facility is part of a multiphase program started in 1983 to address small-break loss-of- coolant accidents (SBLOCAs) specific to Babcock Wilcox (B W) designed plants. MIST is sponsored by the US Nuclear Regulatory Commission, the B W Owners group, the Electric Power Research Institute, and B W. The unique features of the B W</p> <div class="credits"> <p class="dwt_author">J. A. Klingenfus; M. V. Parece</p> <p class="dwt_publisher"></p> <p class="publishDate">1989-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">249</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://eric.ed.gov/?q=Sieber&id=ED276088"> <span id="translatedtitle">Virgin Islands Educational Dissemination <span class="hlt">System</span>. <span class="hlt">Final</span> Report.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p class="result-summary">This document reports on a 5-year project developed by the Department of Education of the U.S. Virgin Islands to create a useful information and technical assistance <span class="hlt">system</span> for professional personnel to bring about educational change and growth. The project was based on the original Interstate Project in Dissemination model (with the exception…</p> <div class="credits"> <p class="dwt_author">Oliver, James M.; And Others</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">250</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011AGUFM.G11A0839F"> <span id="translatedtitle">Strain Distribution across the Terceira (Azores) <span class="hlt">Rift</span> from 13 years of GPS data</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Terceira <span class="hlt">Rift</span> is the westernmost segment of the Nubia-Eurasia plate boundary. Despite the intense investigation carried out along the past decades based on geological, geophysical, and geodetic data, the interpretation of the behaviour of this plate boundary is still controversial in what concerns the location of the triple junction and the strain distribution across the Azores plateau, and in particular, the amount of extension taking place outside the Terceira <span class="hlt">Rift</span>. This is particular difficult to study because geodetic displacements can only be measured on the islands and most of the processes occur offshore. In this work, we use GPS observations acquired between 1997 and 2010 to investigate the strain distribution along the Terceira <span class="hlt">Rift</span>, The number and data-span of the existing permanent stations are still limited and so we combine their velocity field with the solutions derived from episodic data, which averages 7-8 years with 3-4 reoccupations. This allows the definition of mean velocities along a SW-NE transect, crossing Pico-Faial, S. Jorge and Terceira Islands, close to the direction of Eurasia Nubia relative motion, as described by regional geodetic models. <span class="hlt">Finally</span>, the geodetic displacement field is compared with half space elastic modelling, to assess the probable location of <span class="hlt">rifting</span> processes and the amount of extension taking place outside the Terceira <span class="hlt">Rift</span>. This is a contribution from MAREKH (PTDC/MAR/108142/2008) FCT project.</p> <div class="credits"> <p class="dwt_author">Fernandes, R. M.; Miranda, J. M.; Luis, J. M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">251</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/6651208"> <span id="translatedtitle">Stationary flywheel energy storage <span class="hlt">systems</span>. <span class="hlt">Final</span> report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The aim of this <span class="hlt">system</span> study is to find out industrial applications of Stationary Flywheel Energy Accumulators. The economic value for the consumer and the effects on the power supply grid should be investigated. As to overall economy, compensation of short time maximum power out-put seems to be more favorable at the power stations. An additional possibility for energy storage by flywheels is given where otherwise lost energy can be used effectively, according to the successful brake energy storage in vehicles. Under this aspect the future use of flywheels in wind-power-plants seems to be promising. Attractive savings of energy can be obtained by introducing modern flywheel technology for emergency power supply units which are employed for instance in telecommunication <span class="hlt">systems</span>. Especially the application for emergency power supply, in power stations and in combination with wind energy converters needs further investigation.</p> <div class="credits"> <p class="dwt_author">Gilhaus, A.; Hau, E.; Gassner, G.; Huss, G.; Schauberger, H.</p> <p class="dwt_publisher"></p> <p class="publishDate">1982-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">252</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/60348890"> <span id="translatedtitle">Multiloop Integral <span class="hlt">System</span> Test (MIST): <span class="hlt">Final</span> report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The Multiloop Integral <span class="hlt">System</span> Test (MIST) is part of a multiphase program started in 1983 to address small-break loss-of-coolant accidents (SBLOCAs) specific to Babcock Wilcox designed plants. MIST is sponsored by the US Nuclear Regulatory Commission, the Babcock Wilcox Owners Group, the Electric Power Research Institute, and Babcock Wilcox. The unique features of the Babcock Wilcox design, specifically the hot</p> <div class="credits"> <p class="dwt_author">Geissler</p> <p class="dwt_publisher"></p> <p class="publishDate">1990-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">253</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/60412915"> <span id="translatedtitle">Multiloop Integral <span class="hlt">System</span> Test (MIST): <span class="hlt">Final</span> report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The Multiloop Integral <span class="hlt">System</span> Test (MIST) is part of a multiphase program started in 1983 to address small-break loss-of-coolant accidents (SBLOCAs) specific to Babcock Wilcox designed plants. MIST is sponsored by the US Nuclear Regulatory Commission, the Babcock Wilcox Owners Group, the Electric Power Research Institute, and Babcock and Wilcox. The unique features of the Babcock Wilcox design, specifically the</p> <div class="credits"> <p class="dwt_author">Geissler</p> <p class="dwt_publisher"></p> <p class="publishDate">1990-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">254</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/60033290"> <span id="translatedtitle">Multiloop integral <span class="hlt">system</span> test (MIST): <span class="hlt">Final</span> report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The Multiloop Integral <span class="hlt">System</span> Test (MIST) is part of a multiphase program started in 1983 to address small-break loss-of-coolant accidents (SBLOCAs) specific to Babcock and Wilcox designed plants. MIST is sponsored by the US Nuclear Regulatory Commission, the Babcock Wilcox Owners Group, the Electric Power Research Institute, and Babcock and Wilcox. The unique features of the Babcock and Wilcox design,</p> <div class="credits"> <p class="dwt_author">Gloudemans</p> <p class="dwt_publisher"></p> <p class="publishDate">1991-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">255</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/650134"> <span id="translatedtitle">Integrated radwaste treatment <span class="hlt">system</span>. <span class="hlt">Final</span> report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">In May 1988, the West Valley Demonstration Project (WVDP) began pretreating liquid high-level radioactive waste (HLW). This HLW was produced during spent nuclear fuel reprocessing operations that took place at the Western New York Nuclear Service Center from 1966 to 1972. Original reprocessing operations used plutonium/uranium extraction (PUREX) and thorium extraction (THOREX) processes to recover usable isotopes from spent nuclear fuel. The PUREX process produced a nitric acid-based waste stream, which was neutralized by adding sodium hydroxide to it. About two million liters of alkaline liquid HLW produced from PUREX neutralization were stored in an underground carbon steel tank identified as Tank 8D-2. The THOREX process, which was used to reprocess one core of mixed uranium-thorium fuel, resulted in about 31,000 liters of acidic waste. This acidic HLW was stored in an underground stainless steel tank identified as Tank 8D-4. Pretreatment of the HLW was carried out using the Integrated Radwaste Treatment <span class="hlt">System</span> (IRTS), from May 1988 until May 1995. This <span class="hlt">system</span> was designed to decontaminate the liquid HLW, remove salts from it, and encapsulate the resulting waste into a cement waste form that achieved US Nuclear Regulatory Commission (NRC) criteria for low-level waste (LLW) storage and disposal. A thorough discussion of IRTS operations, including all <span class="hlt">systems</span>, subsystems, and components, is presented in US Department of Energy (DOE) Topical Report (DOE/NE/44139-68), Integrated Radwaste Treatment <span class="hlt">System</span> Lessons Learned from 2 1/2 Years of Operation. This document also presents a detailed discussion of lessons learned during the first 2 1/2 years of IRTS operation. This report provides a general discussion of all phases of IRTS operation, and presents additional lessons learned during seven years of IRTS operation.</p> <div class="credits"> <p class="dwt_author">Baker, M.N.; Houston, H.M.</p> <p class="dwt_publisher"></p> <p class="publishDate">1997-10-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">256</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2003AGUFM.S51C0063B"> <span id="translatedtitle">Tomographic Imaging of the Northern Ethiopian <span class="hlt">Rift</span> - a Transition From Continental to Oceanic <span class="hlt">Rifting</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The EAGLE broadband array consisted of 30 sensors distributed over an 250 km x 250 km area of the northern Ethiopian <span class="hlt">Rift</span> in order to study the crust and upper mantle structure of a region of transition from continental to oceanic <span class="hlt">rifting</span>. Analyses of teleseismic relative residual travel times indicate a variation of the order of 1 sec; slower arrivals to the NW of the <span class="hlt">Rift</span> on the uplifted Ethiopian Plateau and faster arrivals to the SE towards the Somali plate. Tomographic inversion of 3614 P-wave and 800 S-wave relative arrival times using the method of VanDecar images a narrow ˜70 km wide low velocity upwelling (1.5% P-wave velocity anomaly), well resolved to 300 km beneath the <span class="hlt">Rift</span> in the southern part of the array. This anomaly broadens with depth northwards into Afar as asthenospheric (oceanic) <span class="hlt">rifting</span> processes begin to take over from the lithospheric (continental) ones prevalent in the south. An off-<span class="hlt">rift</span> axis E-W low velocity anomaly just south of Addis Ababa corresponds to the surface manifestation of a line of Quarternary volcanoes. Interestingly the maximum upper mantle low velocity anomaly is offset by about 25 km to the NW from the location of <span class="hlt">rift</span> magmatic segments. S-wave anomalies show a similar <span class="hlt">rift</span> structure to the P-wave results but are of twice the magnitude.</p> <div class="credits"> <p class="dwt_author">Bastow, I.; Stuart, G.; Kendall, J.; Ebinger, C.; Ayele, A.</p> <p class="dwt_publisher"></p> <p class="publishDate">2003-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">257</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2007AGUFM.C51A0068B"> <span id="translatedtitle">Question of Ages of Cenozoic Volcanic Centers Inferred Beneath the West Antarctic Ice Sheet (WAIS) in the West Antarctic <span class="hlt">Rift</span> <span class="hlt">System</span> (WR) from Coincident Aeromagnetic and Radar Ice Sounding Surveys</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The recently acquired radar ice sounding surveys (Holt, et al., 2006) extending the 1990s Central West Antarctica (CWA) aerogeophysical survey to the Amundsen and Bellingshausen sea coasts allows us to revise a thought experiment reported by Behrendt et al., 1991 from very limited bed elevation data. Were the ice of the WAIS flowing through the WR to be compressed to the density of crustal rock, almost all of the area beneath the WAIS would be at or above sea level, much >1 km elevation. There are only about 10-20% of the very deep areas (such as the Bentley subglacial trench and the Byrd Subglacial Basin) filled with 3-4-km thick ice that would be well below sea level. The age of the 5-7-km high <span class="hlt">rift</span> shoulder bounding the asymmetric WR from northern Victoria Land through the Horlick Mountains (where it diverges from the Transantarctic Mountains) to the Ellsworth Mountains has been reported as old as Cretaceous. Volcanic exposures associated with the West Antarctic <span class="hlt">rift</span> <span class="hlt">system</span> in the present WAIS area extend at least to 34 Ma and the West Antarctic ice sheet has flowed through the <span class="hlt">rift</span> possibly as far back in time as 25 Ma. Active volcanism has been reported for the WR at only a few widely scattered locations, so speculations about present volcanic activity beneath the WAIS are quite uncertain, and it is probably quite rare. The Central West Antarctic aeromagnetic and radar ice sounding survey carried out in the 1990s revealed about 1000 "volcanic centers" characterized by 100-1000 nT shallow source magnetic anomalies, at least 400 of which have associated bed topography. About 80% of these show relief <200 m and have been interpreted as smoothed off as they were erupted (injected) into the moving WAIS. Several kilometer-thick highly magnetic sources are required to fit these anomalies requiring high remanent magnetizations in the present field direction. We interpreted these sources as subvolcanic intrusions which must be younger than about 100 Ma because the Antarctic plate has been in its approximately present position since that time. Eighteen anomalies have >600 bed relief and were interpreted as erupted subaerially at a time when the WAIS was absent. At least one of these subaerially erupted peaks (Mt. Resnik, having 2 km bed relief) was erupted through a magnetic reversal. About 100 "volcanic" anomalies show reversed magnetic polarization indicating these must be at least as old as the Brunes-Matayama reversal at about 780 Ka. Essentially no volcanic rocks or detritus has been reported from the few drill holes that have penetrated the WAIS, although some have speculated, from the presence of smectite recovered from rock cores into the Ross Sea continental shelf, that this mineral has resulted from alteration of volcanic rock erupted beneath the WAIS. We consider the absence of volcanic samples from beneath the WAIS is not evidence of their absence. This seems particularly true considering the long time of the apparently coincident volcanism beneath the WAIS, possibly as great as 25 Ma, and the relatively brief age of the ice presently comprising the WAIS, about 200 Ka at most (e.g. perhaps the bulk of the volcanic centers are >10 Ma). Because none of the volcanic rocks or subvolcanic intrusions inferred to underlie the "volcanic centers" marked by high amplitude anomalies and low relief bed topography has been directly sampled, the question of their age cannot be answered.</p> <div class="credits"> <p class="dwt_author">Behrendt, J. C.; Finn, C. A.; Blankenship, D. D.</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">258</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/836268"> <span id="translatedtitle"><span class="hlt">Final</span> Report of Strongly Interacting Fermion <span class="hlt">Systems</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">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> <div class="credits"> <p class="dwt_author">Wilkins, J. W.</p> <p class="dwt_publisher"></p> <p class="publishDate">2001-06-25</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">259</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ntis.gov/search/product.aspx?ABBR=ADA186603"> <span id="translatedtitle"><span class="hlt">Rift</span> Valley Fever Virus: Molecular Biologic Studies of the M Segment RNA for Application in Disease Prevention.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ntis.gov/search/index.aspx">National Technical Information Service (NTIS)</a></p> <p class="result-summary">The coding capacity and expression strategy of the <span class="hlt">Rift</span> Valley Fever Virus M segment were investigated in detail employing cell-free transcription-translation and recombinant vaccinia virus <span class="hlt">systems</span>. The results indicate that the M segment encodes a primar...</p> <div class="credits"> <p class="dwt_author">M. S. Collett</p> <p class="dwt_publisher"></p> <p class="publishDate">1987-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">260</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ntis.gov/search/product.aspx?ABBR=EPRIEA790"> <span id="translatedtitle">EPRI Water Supply Data Base <span class="hlt">System</span>. <span class="hlt">Final</span> Report, December 1978.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ntis.gov/search/index.aspx">National Technical Information Service (NTIS)</a></p> <p class="result-summary">This is the <span class="hlt">final</span> report for RP762, Water Supply Data Base for R and D Planning. The result of this study is the EPRI water data <span class="hlt">system</span>--a data base, or data dictionary, that describes water data collection efforts. The <span class="hlt">system</span> has two components: (1) a ma...</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate">1978-01-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_12");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' 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src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">261</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/5394816"> <span id="translatedtitle">Superfine Coal Combustion <span class="hlt">System</span>. <span class="hlt">Final</span> report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The objectives of this study are to prepare a conceptual design of a Superfine Coal Combustion <span class="hlt">System</span> (SCCS) and evaluate its technical and economic feasibility for converting oil-fired steam generators to coal firing. In the SCCS, a slurry of coal and water is pressurized and heated to supercritical conditions and rapidly expanded to near atmospheric conditions. The fluid entrapped in the pores of the coal shatters the coal into a superfine condition while leaving the ash size fraction essentially unchanged. The result is a steam-entrained particle mixture with two distinct size and density fractions - light superfine coal and coarser, markedly heavier ash particles. By passing the mixture through a cyclone-type separator, the ash can be collected and the steam/superfine coal mixture allowed to pass to the steam generator coal burners. According to the inventors, this process can remove 75% of the ash and 85% of the sulfur contained in the feed coal. The ''cleaned'' superfine coal will burn with increased flame intensity and reduced flame length and thus can be combusted in existing oil-fired steam generators with minimum slagging, fouling, and derating. 17 refs., 7 figs., 20 tabs.</p> <div class="credits"> <p class="dwt_author">Carli, G.</p> <p class="dwt_publisher"></p> <p class="publishDate">1984-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">262</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2004AGUFM.T33A1347P"> <span id="translatedtitle">Evidence of Melt-Induced Seismic Anisotropy and Magma Assisted <span class="hlt">Rifting</span> in the North Ethiopian <span class="hlt">Rift</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The complex process of the transition from continental to oceanic <span class="hlt">rifting</span> remains poorly understood. The Northern Ethiopian <span class="hlt">Rift</span>, being free from interference from other tectonic processes, is an ideal place to study the continental breakup process. With this in mind, the recent EAGLE experiment saw the deployment of 79 broadband seismometers over an area 250-350km centred on the Northern Ethiopian <span class="hlt">Rift</span>. We investigate the signature of crustal and upper-mantle anisotropy in these data as it provides insights into <span class="hlt">rifting</span> processes. Recent studies employing shear-wave splitting techniques provide strong and consistent evidence for a <span class="hlt">rift</span>-parallel (NNE-SSW) fast anisotropic direction beneath the <span class="hlt">rift</span>. The detailed characteristics of these observations imply a single anisotropic layer confined to the upper 100km. Surface-wave tomography shows that the fast <span class="hlt">rift</span>-parallel directions persist to a depth of 400km beneath a broader area surrounding the <span class="hlt">rift</span>. These observations eliminate a number of plausible causes of anisotropy including plate motion drag, radial mantle-flow in the Afar plume head, mantle flow perpendicular to the <span class="hlt">rift</span> induced by the <span class="hlt">rifting</span> process, or pre-existing frozen-in crystallographic fabric. The observed anisotropy is more likely to be caused by either channeled horizontal mantle-flow along the <span class="hlt">rift</span> axis, which would cause the lattice preferred orientation (LPO) of olivine with the fast ? -axes paralleling the <span class="hlt">rift</span>, or the presence of <span class="hlt">rift</span>-aligned melt-filled pockets (MFP) in the mantle. % SKS-splitting results show that the distribution of the fast anisotropic orientation mimics closely the distribution of strain and magmatism in the <span class="hlt">rift</span>, implying MFP-induced anisotropy. % However, the techniques employed by the studies to date do not provide a means of conclusively separating the two candidate causes of anisotropy. The speeds of horizontally propagating S v and S h waves vary in similar fashions with azimuth for LPO- and MFP-induced anisotropy ( S v ? cos({? }), S h ? cos({2? }), where ? is the azimuth measured from the <span class="hlt">rift</span> axis). However, the the relative change in the two shear-wave velocities is distinctive for LPO- and MFP-induced anisotropy. This provides a powerful tool for distinguishing between the two candidate causes of anisotropy. % We present strong evidence for MFP-induced anisotropy beneath the <span class="hlt">rift</span> in the depth range of 20--60~km, by showing that the azimuthal variation of the speeds of S v and S h waves propagating horizontally through the <span class="hlt">rift</span> area is in good agreement with predicted anisotropy models for vertical <span class="hlt">rift</span>-parallel melt-filled dykes.We obtain shear-velocity models by inverting the group and phase velocity dispersion experienced by a number of local and teleseismic Rayleigh and Love waves with total or inter-station propagation paths crossing the <span class="hlt">rift</span> area with a variety of azimuths. By only using highly coherent waves for the phase-velocity measurements and by applying a phase-matching filtering technique in the group velocity extraction procedure we ensure that our measurements are free from bias introduced by scattering and noise and that our results are reliable and robust.</p> <div class="credits"> <p class="dwt_author">Pilidou, S.; Kendall, J.; Stuart, G.; Bastow, I.</p> <p class="dwt_publisher"></p> <p class="publishDate">2004-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">263</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010GGG....11.8005G"> <span id="translatedtitle">Postspreading <span class="hlt">rifting</span> in the Adare Basin, Antarctica: Regional tectonic consequences</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Extension during the middle Cenozoic (43-26 Ma) in the north end of the West Antarctic <span class="hlt">rift</span> <span class="hlt">system</span> (WARS) is well constrained by seafloor magnetic anomalies formed at the extinct Adare spreading axis. Kinematic solutions for this time interval suggest a southward decrease in relative motion between East and West Antarctica. Here we present multichannel seismic reflection and seafloor mapping data acquired within and near the Adare Basin on a recent geophysical cruise. We have traced the ANTOSTRAT seismic stratigraphic framework from the northwest Ross Sea into the Adare Basin, verified and tied to DSDP drill sites 273 and 274. Our results reveal three distinct periods of tectonic activity. An early localized deformational event took place close to the cessation of seafloor spreading in the Adare Basin (˜24 Ma). It reactivated a few normal faults and initiated the formation of the Adare Trough. A prominent pulse of <span class="hlt">rifting</span> in the early Miocene (˜17 Ma) resulted in normal faulting that initiated tilted blocks. The overall trend of structures was NE-SW, linking the event with the activity outside the basin. It resulted in major uplift of the Adare Trough and marks the last extensional phase of the Adare Basin. Recent volcanic vents (Pliocene to present day) tend to align with the early Miocene structures and the on-land Hallett volcanic province. This latest phase of tectonic activity also involves near-vertical normal faulting (still active in places) with negligible horizontal consequences. The early Miocene extensional event found within the Adare Basin does not require a change in the relative motion between East and West Antarctica. However, the lack of subsequent <span class="hlt">rifting</span> within the Adare Basin coupled with the formation of the Terror <span class="hlt">Rift</span> and an on-land and subice extension within the WARS require a pronounced change in the kinematics of the <span class="hlt">rift</span>. These observations indicate that extension increased southward, therefore suggesting that a major change in relative plate motion took place in the middle Miocene. The late Miocene pole of rotation might have been located north of the Adare Basin, with opposite opening sign compared to the Eocene-Oligocene pole.</p> <div class="credits"> <p class="dwt_author">Granot, R.; Cande, S. C.; Stock, J. M.; Davey, F. J.; Clayton, R. W.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-08-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">264</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3358145"> <span id="translatedtitle">Genome Analysis of <span class="hlt">Rift</span> Valley Fever Virus, Mayotte</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">As further confirmation of a first human case of <span class="hlt">Rift</span> Valley fever in 2007 in Comoros, we isolated <span class="hlt">Rift</span> Valley fever virus in suspected human cases. These viruses are genetically closely linked to the 2006–2007 isolates from Kenya.</p> <div class="credits"> <p class="dwt_author">Zeller, Herve; Grandadam, Marc; Caro, Valerie; Pettinelli, Francois; Bouloy, Michele; Cardinale, Eric; Albina, Emmanuel</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">265</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/51713503"> <span id="translatedtitle">Spatial and Temporal Strain Distribution Along the Central Red Sea <span class="hlt">Rift</span> - A Study of the Hamd-Jizil Basin in Saudi Arabia</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Numerous models exploring the rupturing modes and mechanisms of continental lithosphere are based on geological evidence from the Red Sea\\/Gulf of Suez <span class="hlt">rift</span> <span class="hlt">system</span>. Individually, the Red Sea basin is the prototype for many models of orthogonal continental <span class="hlt">rifting</span>. Despite being a classic example of continental extension, many temporal and spatial strain distribution aspects, as well as the dynamic evolution</p> <div class="credits"> <p class="dwt_author">E. Szymanski; D. Stockli; P. Johnson; F. H. Kattan; A. Al Shamari</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">266</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.agu.org/journals/jb/jb0912/2009JB006303/2009JB006303.pdf"> <span id="translatedtitle">New determinations of 40Ar\\/39Ar isotopic ages and flow volumes for Cenozoic volcanism in the Terror <span class="hlt">Rift</span>, Ross Sea, Antarctica</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">This study provides new determinations of 40Ar\\/39Ar isotopic ages and flow volumes for submarine and subaerial Neogene volcanism developed within the Terror <span class="hlt">Rift</span>, Ross Sea, Antarctica, the youngest segment of the West Antarctic <span class="hlt">Rift</span> <span class="hlt">System</span>. The study is based on the first dredged samples from seven seamounts north of Ross Island, as well as new data from Franklin and Beaufort</p> <div class="credits"> <p class="dwt_author">S. Rilling; S. Mukasa; T. Wilson; L. Lawver; C. Hall</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">267</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/17653189"> <span id="translatedtitle">Variation in styles of <span class="hlt">rifting</span> in the Gulf of California.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Constraints on the structure of <span class="hlt">rifted</span> continental margins and the magmatism resulting from such <span class="hlt">rifting</span> can help refine our understanding of the strength of the lithosphere, the state of the underlying mantle and the transition from <span class="hlt">rifting</span> to seafloor spreading. An important structural classification of <span class="hlt">rifts</span> is by width, with narrow <span class="hlt">rifts</span> thought to form as necking instabilities (where extension rates outpace thermal diffusion) and wide <span class="hlt">rifts</span> thought to require a mechanism to inhibit localization, such as lower-crustal flow in high heat-flow settings. Observations of the magmatism that results from <span class="hlt">rifting</span> range from volcanic margins with two to three times the magmatism predicted from melting models to non-volcanic margins with almost no <span class="hlt">rift</span> or post-<span class="hlt">rift</span> magmatism. Such variations in magmatic activity are commonly attributed to variations in mantle temperature. Here we describe results from the PESCADOR seismic experiment in the southern Gulf of California and present crustal-scale images across three <span class="hlt">rift</span> segments. Over short lateral distances, we observe large differences in <span class="hlt">rifting</span> style and magmatism--from wide <span class="hlt">rifting</span> with minor synchronous magmatism to narrow <span class="hlt">rifting</span> in magmatically robust segments. But many of the factors believed to control structural evolution and magmatism during <span class="hlt">rifting</span> (extension rate, mantle potential temperature and heat flow) tend to vary over larger length scales. We conclude instead that mantle depletion, rather than low mantle temperature, accounts for the observed wide, magma-poor margins, and that mantle fertility and possibly sedimentary insulation, rather than high mantle temperature, account for the observed robust <span class="hlt">rift</span> and post-<span class="hlt">rift</span> magmatism. PMID:17653189</p> <div class="credits"> <p class="dwt_author">Lizarralde, Daniel; Axen, Gary J; Brown, Hillary E; Fletcher, John M; González-Fernández, Antonio; Harding, Alistair J; Holbrook, W Steven; Kent, Graham M; Paramo, Pedro; Sutherland, Fiona; Umhoefer, Paul J</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-07-26</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">268</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011AGUFM.T23D2426N"> <span id="translatedtitle">Models of segmentation along the Terceira <span class="hlt">Rift</span>: implications for the MAR evolution to the south of Azores</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Within the MAREKH project we investigate the Mid-Atlantic Ridge Evolution in the last 20 Ma between Kurchatov and Hayes. Our aim is to extend to the south previous kinematic studies to understand the most important kinematic changes and their impact on the segmentation pattern of the MAR and the formation of the Terceira <span class="hlt">Rift</span>. The Terceira <span class="hlt">rift</span> (TR) is frequently pointed out as unique ultraslow oblique spreading <span class="hlt">system</span> differing from other oceanic <span class="hlt">rifts</span> in that it cuts across relatively old and thick lithosphere. Its pattern of segmentation and the evidence for highly focused magmatism makes it comparable with the continental East African <span class="hlt">Rift</span>. The analogy with the Main Ethiopian <span class="hlt">Rift</span> (MER) is particularly remarkable since both the TR and the MER tectonic settings are characterized by two distinct sets of faults trending 20-30° apart. Findings from analogue modelling by Corti (2008) have shown that <span class="hlt">rift</span> evolution and segmentation in the MER is controlled by <span class="hlt">rift</span> obliquity independently of magmatic processes or changes in plate kinematics. In this work we explore the feasibility of a similar model in the Azores using finite element numerical modeling. The results improve our understanding on the processes of formation and activation of the observed pattern of faulting and <span class="hlt">rift</span> segmentation in the Azores plateau, exploring in particular if the two sets of tectonic trends formed diachronically with activity switching from one to another or if they formed simultaneously like a mixed extensional-shear fracture network, establish the connection between the step-like pattern of the Terceira <span class="hlt">Rift</span> and the segmentation of the MAR to the south of the triple junction and eventually provide constraints on the thermal structure and material properties by determining what combination of model set-ups match the observed patterns. This work was funded by FCT, PTDC/MAR/108142/2008 MAREKH research project. Pest-OE/CTE/LA0019/2011 - IDL</p> <div class="credits"> <p class="dwt_author">Neves, M. L.; Miranda, J. M.; Luis, J. M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">269</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010AGUFM.T31B2158A"> <span id="translatedtitle">Insights into initial stages of <span class="hlt">rifting</span> from seismotectonics and SKS splitting in the North Tanzanian Divergence</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Magmatism and faulting are preponderant processes involved in continental <span class="hlt">rifting</span>. Their interaction, relative importance, and dependence to the rheological properties of the lithosphere and to the timing of <span class="hlt">rifting</span>, remain poorly known. To address this question, we have used the results from a seismological experiment, called SEISMO-TANZ (35 stations, broadband and enlarged-band), launched in the North Tanzanian Divergence (NTD) for 6 months in 2007. The region encompasses one of the youngest parts of the East African <span class="hlt">rift</span> (EAR) and is characterized by the development of the <span class="hlt">rift</span> into the Tanzanian craton. The NTD is often considered as non-volcanic compared to other places in EAR and the lithosphere is highly resistant. More than 2000 local earthquakes were recorded, highlighting active faults and one magmatic intrusion. Inherited structures play a key role as guides for dykes and slips. 26 Focal mechanisms (double-couple hypothesis) were obtained from P-wave polarities and indicate a transtensive deformation in the southern part of the region (Manyara <span class="hlt">rift</span>). The stress inversion performed indicates a stable, well-determined ?3 axis striking ESE-WNW. From 25 teleseismic events recorded during the experiment, we have measured seismic anisotropy (SKS splitting) and present here our last results. Fast polarization directions are quite homogeneously NE-SW and delays times increase from the craton (W) to the Mozambique belt (E). Fossilized anisotropy and dykes or melt-filled lenses alignments would both explain the majority of these observations. We <span class="hlt">finally</span> compare these results with other seismic anisotropy measurements made in EAR and with geodetic and seismotectonic analyses in order to better assess the origin of the strain pattern in this part of the <span class="hlt">rift</span>, and to discuss the respective role of magmatism, faulting and fabrics in the extending lithosphere.</p> <div class="credits"> <p class="dwt_author">Albaric, J.; Barruol, G.; Deverchère, J.; Deschamps, A.; Perrot, J.; Tiberi, C.; Ferdinand, R. W.; Sue, C.; Le Gall, B.; Petit, C.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">270</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/52037913"> <span id="translatedtitle">Strain distribution in the East African <span class="hlt">Rift</span> from GPS measurements</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary"><span class="hlt">Rifting</span> of continental lithosphere is a fundamental process that controls the growth and evolution of continents and the birth of ocean basins. Most <span class="hlt">rifting</span> models assume that stretching results from far-field lithospheric stresses from plate motions, but there is evidence that asthenospheric processes play an active role in <span class="hlt">rifting</span>, possibly through viscous coupling and\\/or the added buoyancy and thermal weakening</p> <div class="credits"> <p class="dwt_author">S. D. Stamps; E. Saria; E. Calais; D. Delvaux; C. Ebinger; L. Combrinck</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">271</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/54910516"> <span id="translatedtitle">Structural evolution history of the Red Sea <span class="hlt">Rift</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The Red Sea <span class="hlt">Rift</span> has been an object of comprehensive studies by several generations of geologists and geophysicists. Many publications and open-file reports provide insights into the geological history of this <span class="hlt">rift</span>. Paleogene and Cretaceous rocks, which are considered to be prerift, are locally exposed at the margins of the Red Sea <span class="hlt">Rift</span>. At the same time, some evidence indicates</p> <div class="credits"> <p class="dwt_author">G. A. F. D'Almeida</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">272</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/5608829"> <span id="translatedtitle">Thermomechanical models of the Rio Grande <span class="hlt">rift</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Fully two-dimensional, coupled thermochemical solutions of a continental <span class="hlt">rift</span> and platform are used to model the crust and mantle structure of a hot, buoyant mantle diapir beneath the Rio Grande <span class="hlt">rift</span>. The thermomechanical model includes both linear and nonlinear laws of the Weertman type relating shear stress and creep strain rate, viscosity which depends on temperature and pressure, and activation energy, temperature-dependent thermal conductivity, temperature-dependent coefficient of thermal expansion, the Boussinesq approximation for thermal bouyancy, material convection using a stress rate that is invariant to rigid rotations, an elastically deformable crust, and a free surface. The model determines the free surface velocities, solid state flow field in the mantle, and viscosity structure of lithosphere and asthenosphere. Regional topography and crustal heat flow are simulated. A suite of symmetric models, assumes continental geotherms on the right and the successively increasing <span class="hlt">rift</span> geotherms on the left. These models predict an asthenospheric flow field which transfers cold material laterally toward the <span class="hlt">rift</span> at > 300 km, hot, buoyant material approx. 200 km wide which ascends vertically at rates of 1 km/my between 175 to 325 km, and spreads laterally away from the <span class="hlt">rift</span> at the base of the lithosphere. Crustal spreading rates are similar to uplift rates. The lithosphere acts as stiff, elastic cap, damping upward motion through decreased velocities of 1 km/10 my and spreading uplift laterally. A parameter study varying material coefficients for the Weertman flow law suggests asthenospheric viscosities of approx. 10/sup 22/ to 10/sup 23/ poise. Similar studies predict crustal viscosities of approx. 10/sup 25/ poise. The buoyant process of mantle flow narrows and concentrates heat transport beneath the <span class="hlt">rift</span>, increases upward velocity, and broadly arches the lithosphere. 10 figures, 1 table.</p> <div class="credits"> <p class="dwt_author">Bridwell, R.J.; Anderson, C.A.</p> <p class="dwt_publisher"></p> <p class="publishDate">1980-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">273</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://pubs.er.usgs.gov/publication/70016871"> <span id="translatedtitle">Deep magma body beneath the summit and <span class="hlt">rift</span> zones of Kilauea Volcano, Hawaii</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p class="result-summary">A magnitude 7.2 earthquake in 1975 caused the south flank of Kilauea Volcano, Hawaii, to move seaward in response to slippage along a deep fault. Since then, a large part of the volcano's edifice has been adjusting to this perturbation. The summit of Kilauea extended at a rate of 0.26 meter per year until 1983, the south flank uplifted more than 0.5 meter, and the axes of both the volcano's <span class="hlt">rift</span> zones extended and subsided; the summit continues to subside. These ground-surface motions have been remarkably steady and much more widespread than those caused by either recurrent inflation and deflation of the summit magma chamber or the episodic propagation of dikes into the <span class="hlt">rift</span> zones. Kilauea's magmatic <span class="hlt">system</span> is, therefore, probably deeper and more extensive than previously thought; the summit and both <span class="hlt">rift</span> zones may be underlain by a thick, near vertical dike-like magma <span class="hlt">system</span> at a depth of 3 to 9 kilometers.</p> <div class="credits"> <p class="dwt_author">Delaney, P. T.; Fiske, R. S.; Miklius, A.; Okamura, A. T.; Sako, M. K.</p> <p class="dwt_publisher"></p> <p class="publishDate">1990-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">274</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.agu.org/journals/jb/jb0712/2006JB004795/2006JB004795.pdf"> <span id="translatedtitle"><span class="hlt">Rifting</span> and lower crustal reflectivity: A case study of the intracratonic Dniepr-Donets <span class="hlt">rift</span> zone, Ukraine</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Intracratonic <span class="hlt">rifting</span>, caused by late Devonian extensional stresses in the East European Craton, created the largest <span class="hlt">rift</span> zone in Europe, the Pripyat-Dniepr-Donets <span class="hlt">rift</span> (southeast Ukraine). The <span class="hlt">rift</span> basin is approximately 2000 km long, up to 170 km wide, and 22 km deep. Wide-angle refraction and reflection seismic data from the Donbas Basin deep seismic Refraction and Reflection Experiments (DOBRE'99) project</p> <div class="credits"> <p class="dwt_author">Stig B. Lyngsie; Hans Thybo; Rasmus Lang</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">275</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3311189"> <span id="translatedtitle">Molecular Epidemiology of <span class="hlt">Rift</span> Valley Fever Virus</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">Phylogenetic relationships were examined for 198 <span class="hlt">Rift</span> Valley fever virus isolates and 5 derived strains obtained from various sources in Saudi Arabia and 16 countries in Africa during a 67-year period (1944–2010). A maximum-likelihood tree prepared with sequence data for a 490-nt section of the Gn glycoprotein gene showed that 95 unique sequences sorted into 15 lineages. A 2010 isolate from a patient in South Africa potentially exposed to co-infection with live animal vaccine and wild virus was a reassortant. The potential influence of large-scale use of live animal vaccine on evolution of <span class="hlt">Rift</span> Valley fever virus is discussed.</p> <div class="credits"> <p class="dwt_author">Grobbelaar, Antoinette A.; Weyer, Jacqueline; Leman, Patricia A.; Kemp, Alan; Paweska, Janusz T.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">276</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/60472037"> <span id="translatedtitle">Revenue-metering device for HVDC <span class="hlt">systems</span>. <span class="hlt">Final</span> report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">This <span class="hlt">final</span> report describes a digital dc revenue metering device for HVDC <span class="hlt">systems</span> developed by Washington State University researchers under a contract with the Electric Power Research Institute. The device was installed at the Sylmar Converter Station of the Los Angeles Department of Water and Power in November 1981, and has been operating satisfactorily for over 20 months. It uses</p> <div class="credits"> <p class="dwt_author">E. O. Schweitzer; M. Ando; A. Aliaga; R. Baker; D. Seamans</p> <p class="dwt_publisher"></p> <p class="publishDate">1984-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">277</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://eric.ed.gov/?q=ORem%27&pg=5&id=ED244581"> <span id="translatedtitle">Instructional <span class="hlt">Systems</span> Development Model for Interactive Videodisc. <span class="hlt">Final</span> Report.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p class="result-summary">|This third and <span class="hlt">final</span> report on a 3-year project, which developed authoring and production procedures for interactive videodisc based on the Interservice Procedures for Instructional <span class="hlt">Systems</span> Development (IPISD), reviews the current state of the art, provides an overview of the project, and describes two videodiscs made for the project and the…</p> <div class="credits"> <p class="dwt_author">Campbell, J. Olin; And Others</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">278</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/842264"> <span id="translatedtitle">Study of a <span class="hlt">final</span> focus <span class="hlt">system</span> for high intensity beams</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The NTX experiment at the Heavy Ion Fusion Virtual National Laboratory is exploring the performance of neutralized <span class="hlt">final</span> focus <span class="hlt">systems</span> for high perveance heavy ion beams. The <span class="hlt">final</span> focus scenario in an HIF driver consists of several large aperture quadrupole magnets followed by a drift section in which the beam space charge is neutralized by a plasma. This beam is required to hit a millimeter-sized target spot at the end of the drift section. The objective of the NTX experiments and associated theory and simulations is to study the various physical mechanisms that determine the <span class="hlt">final</span> spot size (radius r{sub s}) at a given distance (f) from the end of the last quadrupole. In a fusion driver, f is the standoff distance required to keep the chamber wall and superconducting magnets properly protected. The NTX <span class="hlt">final</span> quadrupole focusing <span class="hlt">system</span> produces a converging beam at the entrance to the neutralized drift section where it focuses to a small spot. The <span class="hlt">final</span> spot is determined by the conditions of the beam entering the quadrupole section, the beam dynamics in the magnetic lattice, and the plasma neutralization dynamics in the drift section. The main issues are the control of emittance growth due to high order fields from magnetic multipoles and image fields. In this paper, we will describe the theoretical and experimental aspects of the beam dynamics in the quadrupole lattice, and how these physical effects influence the <span class="hlt">final</span> beam size. In particular, we present theoretical and experimental results on the dependence of <span class="hlt">final</span> spot size on geometric aberrations and perveance.</p> <div class="credits"> <p class="dwt_author">Henestroza, Enrique; Eylon, Shmuel; Roy, Prabir K.; Yu, Simon S.; Bieniosek, Frank M.; Shuman, Derek B.; Waldron, William L.</p> <p class="dwt_publisher"></p> <p class="publishDate">2004-06-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">279</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/1982Natur.298..736C"> <span id="translatedtitle">Oligo-Miocene <span class="hlt">rift</span> of Sardinia and the early history of the Western Mediterranean Basin</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The geodynamic evolution of the Western Mediterranean Basin, in spite of many studies, is still uncertain. There is some consensus for interpreting this basin as a kind of small oceanic marginal basin. Its opening has generally been related to a subduction process which was active during the Oligocene-Miocene somewhere east of Sardinia-Corsica1-7. As the margins of the basin are deeply buried below Miocene-to-present sediments, direct lithological and stratigraphical data which could explain the events responsible for its formation are rare8-10 or missing altogether. To obtain such data, detailed field studies have been undertaken in Sardinia (Fig. 1), and the first results are presented here. This approach is justified by the fact that in that island, Oligocene and Miocene sediments were deposited in a <span class="hlt">rift</span> (fossa tettonica sarda of Verdabasso11), which is the easternmost arm of the complex <span class="hlt">rift</span> <span class="hlt">system</span> that affected the European plate during Oligocene and Miocene times. One of these arms evolved towards a small oceanic basin-the Western Mediterranean or Algero-Provençal Basin-while others such as the Gulf of Valencia and the Sardinia <span class="hlt">rift</span> aborted and remained at the <span class="hlt">rift</span> stage. Its exceptional exposures make it possible to examine the Sardinia <span class="hlt">rift</span> to clarify the sequence of events which created it, and to establish a sedimentological model which we believe is directly applicable to the Western Mediterranean Basin.</p> <div class="credits"> <p class="dwt_author">Cherchi, A.</p> <p class="dwt_publisher"></p> <p class="publishDate">1982-08-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">280</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://geo.mff.cuni.cz/~jz/papers/bernard_etal_tect2006.pdf"> <span id="translatedtitle">Seismicity, deformation and seismic hazard in the western <span class="hlt">rift</span> of Corinth: New insights from the Corinth <span class="hlt">Rift</span> Laboratory (CRL)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">This paper presents the main recent results obtained by the seismological and geophysical monitoring arrays in operation in the <span class="hlt">rift</span> of Corinth, Greece. The Corinth <span class="hlt">Rift</span> Laboratory (CRL) is set up near the western end of the <span class="hlt">rift</span>, where instrumental seismicity and strain rate is highest. The seismicity is clustered between 5 and 10 km, defining an active layer, gently dipping</p> <div class="credits"> <p class="dwt_author">P. Bernard; H. Lyon-Caen; P. Briole; A. Deschamps; F. Boudin; K. Makropoulos; P. Papadimitriou; F. Lemeille; G. Patau; H. Billiris; D. Paradissis; K. Papazissi; H. Castarède; O. Charade; A. Nercessian; A. Avallone; F. Pacchiani; J. Zahradnik; S. Sacks; A. Linde</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-01-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_13");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a onClick='return showDiv("page_3");' href="#">3</a> <a onClick='return showDiv("page_4");' 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onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">281</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://homepages.see.leeds.ac.uk/~eardke/2006a_keir.pdf"> <span id="translatedtitle">Strain accommodation by magmatism and faulting as <span class="hlt">rifting</span> proceeds to breakup: Seismicity of the northern Ethiopian <span class="hlt">rift</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The volcanically active Main Ethiopian <span class="hlt">rift</span> (MER) marks the transition from continental <span class="hlt">rifting</span> in the East African <span class="hlt">rift</span> to incipient seafloor spreading in Afar. We use new seismicity data to investigate the distribution of strain and its relationship with magmatism immediately prior to continental breakup. From October 2001 to January 2003, seismicity was recorded by up to 179 broadband instruments</p> <div class="credits"> <p class="dwt_author">Derek Keir; C. J. Ebinger; G. W. Stuart; E. Daly; A. Ayele</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">282</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/42062950"> <span id="translatedtitle">Transform and <span class="hlt">rift</span> structure of Paleogene crust near Resolution Ridge, Tasman Sea, southwest New Zealand</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">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</p> <div class="credits"> <p class="dwt_author">Daniel H. N. Barker; Ray Wood; Rupert Sutherland</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">283</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=198247"> <span id="translatedtitle">A REVIEW OF ISSUES AND CONCERNS OF <span class="hlt">RIFT</span> VALLEY FEVER VIRUS, A POTENTIAL EMERGING THREAT TO LIVESTOCK, WILDLIFE, AND HUMANS IN THE U.S., AND A GIS EARLY WARNING <span class="hlt">SYSTEM</span> FOR RVF VECTORS</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p class="result-summary"><span class="hlt">Rift</span> Valley fever (RVF) virus is a mosquito-borne zoonotic hemorrhagic disease that causes 100% abortions in ungulates such as cattle, sheep, and goats, and is often fatal to young animals. Though currently confined mainly to Africa this disease could be introduced into the U.S. and spread via mosq...</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">284</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=198246"> <span id="translatedtitle"><span class="hlt">RIFT</span> VALLEY FEVER VIRUS: AN EMERGING THREAT TO WILDLIFE, LIVESTOCK, AND HUMANS IN THE U.S. - A REVIEW OF ISSUES AND CONCERNS, AND A GIS EARLY WARNING <span class="hlt">SYSTEM</span> FOR RVF VECTORS</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p class="result-summary"><span class="hlt">Rift</span> Valley fever (RVF) virus is a mosquito-borne zoonotic hemorrhagic disease that causes 100% abortions in ungulates such as cattle, sheep, and goats, and is often fatal to young animals. Though currently confined mainly to Africa this disease could be introduced into the U.S. and spread via mosq...</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">285</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/56422580"> <span id="translatedtitle">Geophysical evidence of a Large Igneous Province (LIP) in the West Antarctic <span class="hlt">Rift</span> <span class="hlt">System</span> (WARS), and its potential influence on the stability of the West Antarctic Ice Sheet (WAIS)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The WAIS flows through the volcanically active WARS. The inland <span class="hlt">rift</span> shoulder ranges from 4-5 km elevation, (5-7 km relief, the greatest in the world); it is coincident with the Transantarctic Mountains from northern Victoria land bordering the Ross Sea, south along the west and south side of the Ross Ice Shelf to the Horlick Mountains. It forms the boundary</p> <div class="credits"> <p class="dwt_author">J. C. Behrendt</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">286</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.springerlink.com/index/3658u820kk518577.pdf"> <span id="translatedtitle">Middle Miocene to Pleistocene sedimentary record of <span class="hlt">rift</span> evolution in the southern Albert <span class="hlt">Rift</span> (Uganda)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">This study presents an almost complete Middle Miocene to Pleistocene sequence of synrift sediments in the western branch of\\u000a the East African <span class="hlt">Rift</span>. The studied succession is exposed in several patches on an eastward tilted block between the northern\\u000a tip of the Rwenzori Block and the eastern shoulder of the Albert <span class="hlt">Rift</span>. In this position, it reaches a maximum thickness</p> <div class="credits"> <p class="dwt_author">S. Roller; J. Hornung; M. Hinderer; I. Ssemmanda</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">287</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/5594528"> <span id="translatedtitle">Stratigraphy and <span class="hlt">rifting</span> history of the Mesozoic-Cenozoic Anza <span class="hlt">rift</span>, Kenya</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Lithological and compositional relationships, thicknesses, and palynological data from drilling cuttings from five wells in the Anza <span class="hlt">rift</span>, Kenya, indicate active <span class="hlt">rifting</span> during the Late Cretaceous and Eocene-Oligocene. The earlier <span class="hlt">rifting</span> possibly started in the Santonian-Coniacian, primarily occurred in the Campanian, and probably extended into the Maastrichtian. Anza <span class="hlt">rift</span> sedimentation was in lacustrine, lacustrine-deltaic, fluvial, and flood-basin environments. Inferred synrift intervals in wells are shalier, thicker, more compositionally immature, and more poorly sorted than Lower Cretaceous ( )-lower Upper Cretaceous and upper Oligocene( )-Miocene interrift deposits. Synrift sandstone is mostly feldspathic or arkosic wacke. Sandstone deposited in the Anza basin during nonrift periods is mostly quartz arenite, and is coarser and has a high proportion of probable fluvial deposits relative to other facies. Volcanic debris is absent in sedimentary strata older than Pliocene-Holocene, although small Cretaceous intrusions are present in the basin. Cretaceous sandstone is cemented in places by laumontite, possibly recording Campanian extension. Early Cretaceous history of the Anza basin is poorly known because of the limited strata sampled; Jurassic units were not reached. Cretaceous <span class="hlt">rifting</span> in the Anza basin was synchronous with <span class="hlt">rifting</span> in Sudan and with the breakup and separation of South America and Africa; these events likely were related. Eocene-Oligocene extension in the Anza basin reflects different stresses. The transition from active <span class="hlt">rifting</span> to passive subsidence in the Anza basin at the end of the Neogene, in turn, records a reconfigured response of east African plates to stresses and is correlated with formation of the East Africa <span class="hlt">rift</span>.</p> <div class="credits"> <p class="dwt_author">Winn, R.D. Jr.; Steinmetz, J.C. (Marathon Oil Co., Littleton, CO (United States)); Kerekgyarto, W.L. (Marathon Oil Co., Houston, TX (United States))</p> <p class="dwt_publisher"></p> <p class="publishDate">1993-11-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">288</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ntis.gov/search/product.aspx?ABBR=DE84006920"> <span id="translatedtitle">Small Wind <span class="hlt">Systems</span> (Field Evaluation). Volume IV. Small Wind <span class="hlt">Systems</span> Performance Data. <span class="hlt">Final</span> Report.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ntis.gov/search/index.aspx">National Technical Information Service (NTIS)</a></p> <p class="result-summary">This <span class="hlt">final</span> report describes the operation, management, and results of the Field Evaluation Program (FEP) for Small Wind <span class="hlt">Systems</span>, which was operated by Rockwell International Energy <span class="hlt">Systems</span> Group for the US Department of Energy from the Rocky Flats Wind En...</p> <div class="credits"> <p class="dwt_author">J. M. Sherman D. M. Dodge W. S. Bollmeier</p> <p class="dwt_publisher"></p> <p class="publishDate">1983-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">289</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/42051223"> <span id="translatedtitle">Tertiary arc <span class="hlt">rifting</span> in northern Luzon, Philippines</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The North Luzon terrane (NLT), comprising the section of Luzon north of the Philippine Fault, is one of the largest arc terranes in the Philippine Archipelago. Numerous features suggest that the NLT is a late Oligocene to early Miocene analogue for the processes in the modern intra-arc <span class="hlt">rift</span> zone at the northern end of the Mariana Trough. First, the NLT</p> <div class="credits"> <p class="dwt_author">Federico F. Florendo</p> <p class="dwt_publisher"></p> <p class="publishDate">1994-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">290</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3310676"> <span id="translatedtitle">Unexpected <span class="hlt">Rift</span> Valley Fever Outbreak, Northern Mauritania</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">During September–October 2010, an unprecedented outbreak of <span class="hlt">Rift</span> Valley fever was reported in the northern Sahelian region of Mauritania after exceptionally heavy rainfall. Camels probably played a central role in the local amplification of the virus. We describe the main clinical signs (hemorrhagic fever, icterus, and nervous symptoms) observed during the outbreak.</p> <div class="credits"> <p class="dwt_author">El Mamy, Ahmed B. Ould; Baba, Mohamed Ould; Barry, Yahya; Isselmou, Katia; Dia, Mamadou L.; Hampate, Ba; Diallo, Mamadou Y.; El Kory, Mohamed Ould Brahim; Diop, Mariam; Lo, Modou Moustapha; Thiongane, Yaya; Bengoumi, Mohammed; Puech, Lilian; Plee, Ludovic; Claes, Filip; Doumbia, Baba</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">291</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=264014"> <span id="translatedtitle"><span class="hlt">Rift</span> Valley fever: A neglected zoonotic disease?</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p class="result-summary"><span class="hlt">Rift</span> Valley fever (RVF) is a serious viral disease of animals and humans in Africa and the Middle East that is transmitted by mosquitoes. First isolated in Kenya during an outbreak in 1930, subsequent outbreaks have had a significant impact on animal and human health, as well as national economies. ...</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">292</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=286155"> <span id="translatedtitle">Diagnostic approaches for <span class="hlt">Rift</span> Valley Fever</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p class="result-summary">Disease outbreaks caused by arthropod-borne animal viruses (arboviruses) resulting in significant livestock and economic losses world-wide appear to be increasing. <span class="hlt">Rift</span> Valley fever (RVF) virus (RVFV) is an important arbovirus that causes lethal disease in cattle, camels, sheep and goats in Sub-Saha...</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">293</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/15650736"> <span id="translatedtitle">Magma-assisted <span class="hlt">rifting</span> in Ethiopia.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">The <span class="hlt">rifting</span> of continents and evolution of ocean basins is a fundamental component of plate tectonics, yet the process of continental break-up remains controversial. Plate driving forces have been estimated to be as much as an order of magnitude smaller than those required to rupture thick continental lithosphere. However, Buck has proposed that lithospheric heating by mantle upwelling and related magma production could promote lithospheric rupture at much lower stresses. Such models of mechanical versus magma-assisted extension can be tested, because they predict different temporal and spatial patterns of crustal and upper-mantle structure. Changes in plate deformation produce strain-enhanced crystal alignment and increased melt production within the upper mantle, both of which can cause seismic anisotropy. The Northern Ethiopian <span class="hlt">Rift</span> is an ideal place to test break-up models because it formed in cratonic lithosphere with minor far-field plate stresses. Here we present evidence of seismic anisotropy in the upper mantle of this <span class="hlt">rift</span> zone using observations of shear-wave splitting. Our observations, together with recent geological data, indicate a strong component of melt-induced anisotropy with only minor crustal stretching, supporting the magma-assisted <span class="hlt">rifting</span> model in this area of initially cold, thick continental lithosphere. PMID:15650736</p> <div class="credits"> <p class="dwt_author">Kendall, J-M; Stuart, G W; Ebinger, C J; Bastow, I D; Keir, D</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-01-13</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">294</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/6639361"> <span id="translatedtitle">Longitudinal evolution of Suez <span class="hlt">rift</span> structure, Egypt</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">A three-dimensional study of the structure of the Suez <span class="hlt">Rift</span> has been carried out using field and subsurface data in an attempt to determine the role of transverse faults and the longitudinal evolution of the <span class="hlt">rift</span>. As in most intracontinental <span class="hlt">rifts</span>, the structure of the Gulf of Suez area is governed by normal faults and tilted blocks, whose crests constitute the main target of exploratory wells. The fault pattern consists of two major sets of trends: (1) longitudinal faults parallel with the <span class="hlt">rift</span> axis and created in an extensional regime, trending east-northeast-west-southwest, and (2) transverse faults with north-south to north-northeast-south-southwest dominant trend. The transverse faults are inherited passive discontinuities, whereas most of the longitudinal faults were created during the Neogene in a purely extensional regime. Both sets were simultaneously active, producing a zigzag pattern and rhombic-shaped blocks. The transverse faults can show horizontal strike-slip components and act as relays between major normal faults.</p> <div class="credits"> <p class="dwt_author">Colletta, B.; Le Quellec, P.; Letouzey, J.; Moretti, I.</p> <p class="dwt_publisher"></p> <p class="publishDate">1988-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">295</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/19331733"> <span id="translatedtitle"><span class="hlt">Rift</span> Valley fever, Mayotte, 2007-2008.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">After the 2006-2007 epidemic wave of <span class="hlt">Rift</span> Valley fever (RVF) in East Africa and its circulation in the Comoros, laboratory case-finding of RVF was conducted in Mayotte from September 2007 through May 2008. Ten recent human RVF cases were detected, which confirms the indigenous transmission of RFV virus in Mayotte. PMID:19331733</p> <div class="credits"> <p class="dwt_author">Sissoko, Daouda; Giry, Claude; Gabrie, Philippe; Tarantola, Arnaud; Pettinelli, François; Collet, Louis; D'Ortenzio, Eric; Renault, Philippe; Pierre, Vincent</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-04-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">296</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=188099"> <span id="translatedtitle"><span class="hlt">RIFT</span> VALLEY FEVER POTENTIAL, ARABIAN PENINSULA</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p class="result-summary"><span class="hlt">Rift</span> Valley fever (RVF) was first confirmed outside of Africa in September 2000. This outbreak, which occurred in southwestern coastal Saudi Arabia and neighboring coastal areas of Yemen, followed elevated rainfall levels in nearby highlands which flooded the coastal areas, providing ideal environm...</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">297</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/54276274"> <span id="translatedtitle">The Tectonics of the Albertlne <span class="hlt">Rift</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">IT has been represented to me that misconception with regard to this matter, so far as my own views are concerned, may arise in consequence of my passing, without comment, some remarks made by Prof. J. W. Gregory in his able review of Prof. Bailey Willis's book, ``Living Africa''.1 Gregory quotes my early description of the local <span class="hlt">rift</span> valleys correctly</p> <div class="credits"> <p class="dwt_author">E. J. Wayland</p> <p class="dwt_publisher"></p> <p class="publishDate">1932-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">298</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/54331730"> <span id="translatedtitle">The <span class="hlt">rifted</span> margin of Saudi Arabia</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The structure of <span class="hlt">rifted</span> continental margins has always been of great scientific interest, and now, with dwindling economic oil deposits, these complex geological features assume practical importance as well. The ocean-continent transition is, by definition, laterally heterogeneous and likely to be extremely complicated. The southernmost shotpoints (4, 5, and 6) in the U.S. Geological Survey seismic refraction profile in the</p> <div class="credits"> <p class="dwt_author">J. S. McClain; J. A. Orcutt</p> <p class="dwt_publisher"></p> <p class="publishDate">1984-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">299</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012EGUGA..14.1510K"> <span id="translatedtitle">Along-<span class="hlt">rift</span> variations in style of deformation at the Red Sea <span class="hlt">rift</span> in Afar</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Continental breakup and the transition to seafloor spreading is characterized by extensional faulting, thinning of the lithosphere and, at magmatic margins, voluminous intrusive and extrusive magmatism. It is difficult to discriminate between different mechanisms and timing of extension and magmatism at ancient continental margins because the continent-ocean transition is buried beneath thick layers of volcanic and sedimentary rocks and the tectonic activity that characterized breakup has ceased. Instead, the timing of these mechanisms is inferred from theoretical models or from the geological record preserved at the fully developed, ancient <span class="hlt">rifted</span> margins. Ongoing <span class="hlt">rifting</span> in the Red Sea <span class="hlt">rift</span> in Afar offers a unique opportunity to address these problems because it exposes subaerially the transition between continental <span class="hlt">rifting</span> and seafloor spreading. Here we present evidence from seismicity, InSAR, controlled source seismology, and volcanology for along-<span class="hlt">rift</span> variations in style of deformation in Afar. We show that although intrusion of magma maintains crustal thickness during the early stages of the continent-ocean transition, subsidence of the <span class="hlt">rift</span> below sea level, and eruption of voluminous basalt flows, is initiated by late-stage and rapid mechanical deformation (faulting in upper crust and stretching in the lower crust) of the heavily intruded, weakened plate just before the onset of seafloor spreading. We thus conclude that faulting, stretching and magma intrusion are each important, but at different times during breakup.</p> <div class="credits"> <p class="dwt_author">Keir, D.; Bastow, I.; Pagli, C.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-04-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">300</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/1986JGR....91.6142K"> <span id="translatedtitle">Introduction to Special Section on the Rio Grande <span class="hlt">Rift</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">With the aid of a Penrose Conference in 1974 and an international <span class="hlt">rift</span> conference held in 1978 in Santa Fe, New Mexico, the Rio Grande <span class="hlt">rift</span> has become widely recognized as a major Cenozoic continental <span class="hlt">rift</span> zone. As a result of the 1978 Santa Fe meeting, the American Geophysical Union published a special volume of papers concerned with the Rio Grande <span class="hlt">rift</span> [Riecker, 1979], and the New Mexico Geological Society recently published another volume focused on this <span class="hlt">rift</span> [Baldridge et al., 1984]. These volumes are a manifestation of the research activity which lead to the formation of the Rio Grande <span class="hlt">rift</span> consortium whose purpose is to foster <span class="hlt">rift</span>-related research and communication. This organization has sponsored several special sessions at geological and geophysical meetings and has generally increased the awareness of this important feature.</p> <div class="credits"> <p class="dwt_author">Keller, G. R.</p> <p class="dwt_publisher"></p> <p class="publishDate">1986-05-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_14");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a onClick='return showDiv("page_3");' href="#">3</a> <a onClick='return showDiv("page_4");' 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onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">301</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/11557977"> <span id="translatedtitle">Evolution of magma-poor continental margins from <span class="hlt">rifting</span> to seafloor spreading.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">The <span class="hlt">rifting</span> of continents involves faulting (tectonism) and magmatism, which reflect the strain-rate and temperature dependent processes of solid-state deformation and decompression melting within the Earth. Most models of this <span class="hlt">rifting</span> have treated tectonism and magmatism separately, and few numerical simulations have attempted to include continental break-up and melting, let alone describe how continental <span class="hlt">rifting</span> evolves into seafloor spreading. Models of this evolution conventionally juxtapose continental and oceanic crust. Here we present observations that support the existence of a zone of exhumed continental mantle, several tens of kilometres wide, between oceanic and continental crust on continental margins where magma-poor <span class="hlt">rifting</span> has taken place. We present geophysical and geological observations from the west Iberia margin, and geological mapping of margins of the former Tethys ocean now exposed in the Alps. We use these complementary findings to propose a conceptual model that focuses on the <span class="hlt">final</span> stage of continental extension and break-up, and the creation of a zone of exhumed continental mantle that evolves oceanward into seafloor spreading. We conclude that the evolving stress and thermal fields are constrained by a rising and narrowing ridge of asthenospheric mantle, and that magmatism and rates of extension systematically increase oceanward. PMID:11557977</p> <div class="credits"> <p class="dwt_author">Whitmarsh, R B; Manatschal, G; Minshull, T A</p> <p class="dwt_publisher"></p> <p class="publishDate">2001-09-13</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">302</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2001Natur.413..150W"> <span id="translatedtitle">Evolution of magma-poor continental margins from <span class="hlt">rifting</span> to seafloor spreading</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The <span class="hlt">rifting</span> of continents involves faulting (tectonism) and magmatism, which reflect the strain-rate and temperature dependent processes of solid-state deformation and decompression melting within the Earth. Most models of this <span class="hlt">rifting</span> have treated tectonism and magmatism separately, and few numerical simulations have attempted to include continental break-up and melting, let alone describe how continental <span class="hlt">rifting</span> evolves into seafloor spreading. Models of this evolution conventionally juxtapose continental and oceanic crust. Here we present observations that support the existence of a zone of exhumed continental mantle, several tens of kilometres wide, between oceanic and continental crust on continental margins where magma-poor <span class="hlt">rifting</span> has taken place. We present geophysical and geological observations from the west Iberia margin, and geological mapping of margins of the former Tethys ocean now exposed in the Alps. We use these complementary findings to propose a conceptual model that focuses on the <span class="hlt">final</span> stage of continental extension and break-up, and the creation of a zone of exhumed continental mantle that evolves oceanward into seafloor spreading. We conclude that the evolving stress and thermal fields are constrained by a rising and narrowing ridge of asthenospheric mantle, and that magmatism and rates of extension systematically increase oceanward.</p> <div class="credits"> <p class="dwt_author">Whitmarsh, R. B.; Manatschal, G.; Minshull, T. A.</p> <p class="dwt_publisher"></p> <p class="publishDate">2001-09-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">303</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/6198169"> <span id="translatedtitle">North Sinai-Levant <span class="hlt">rift</span>-transform continental margin</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The passive continental margin of northern Egypt and the Levant coast formed during the Early mesozoic as the relatively small Anatolia plate broke away from northern Africa. The oceanic basin of the eastern Mediterranean and the unusual right-angle bend in the North Sinai-Levant shelf margin are both products of plate separation along a <span class="hlt">rift</span>-transform fracture <span class="hlt">system</span>, the south arm of Tethys. The north-south trending Levant transform margin is considerably narrower than the east-west trending <span class="hlt">rift</span> margin of northern Egypt. Both exhibit similar facies and depositional histories through the mid-Tertiary. Analysis of subsurface data and published reports of the regional stratigraphy point to a three-stage tectonic evolution of this passive margin. The Triassic through mid-Cretaceous was marked by crustal breakup followed by rapid rotational subsidence of the shelf margins about hinge lines located just south and east of the present shorelines. Reef carbonates localized on the shelf edge separated a deep marine basin to the north from a deltaic-shallow marine platform to the south and east. In the Late Cretaceous-Early Tertiary, inversion of earlier formed half-grabens produced broad anticlinal upwarps of the Syrian Arc on the shelf margin that locally influenced facies patterns. The episode of inversion corresponds with the onset of northward subduction of the Africa plate beneath southern Asia. Beginning in the Oligocene and continuing to the present, there has been renewed subsidence of the North Sinai shelf margin beneath thick, outward building clastic wedges. The source of this large volume of sediment is the updomed and erosionally stripped margins of the Suez-Red Sea <span class="hlt">Rift</span> and the redirected Nile River.</p> <div class="credits"> <p class="dwt_author">Ressetar, R.; Schamel, S.; Travis, C.J.</p> <p class="dwt_publisher"></p> <p class="publishDate">1985-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">304</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/663481"> <span id="translatedtitle">Simulated coal gas MCFC power plant <span class="hlt">system</span> verification. <span class="hlt">Final</span> report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">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> <div class="credits"> <p class="dwt_author">NONE</p> <p class="dwt_publisher"></p> <p class="publishDate">1998-07-30</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">305</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/627600"> <span id="translatedtitle">The <span class="hlt">final</span> analysis Little Leo: A <span class="hlt">system</span> and service overview</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">There is an emerging commercial space industry consisting of constellations of low earth orbiting satellites to that will provide global telecommunications services. Within the set of proposed low earth orbiting satellite <span class="hlt">systems</span>, there exists two distinct classes. One class provides high bandwidth digital voice and data services, and the other provides narrowband store and forward digital data services. The digital data service <span class="hlt">systems</span> are called Little LEOs or Infosats. These <span class="hlt">systems</span> will provide a variety of personal, business, environmental, and industrial digital data services on a global scale. Infosat <span class="hlt">systems</span> provide a niche telecommunications infrastructure that benefit industries and governments of the world whether developing or industrialized; geographically homogeneous or diverse; or low, middle, or high income. The flexible nature of the service allows it to be applied in many ways to meet changing needs. This paper provides an overview of the <span class="hlt">Final</span> Analysis Infosat <span class="hlt">system</span>. {copyright} {ital 1997 American Institute of Physics.}</p> <div class="credits"> <p class="dwt_author">Fatig, M. [Final Analysis Inc. 9701-E Philadelphia Ct. Lanham, Maryland20706-4400 (United States)</p> <p class="dwt_publisher"></p> <p class="publishDate">1997-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">306</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/1997AIPC..387..969F"> <span id="translatedtitle">The <span class="hlt">final</span> analysis Little Leo: A <span class="hlt">system</span> and service overview</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">There is an emerging commercial space industry consisting of constellations of low earth orbiting satellites to that will provide global telecommunications services. Within the set of proposed low earth orbiting satellite <span class="hlt">systems</span>, there exists two distinct classes. One class provides high bandwidth digital voice and data services, and the other provides narrowband store and forward digital data services. The digital data service <span class="hlt">systems</span> are called Little LEOs or Infosats. These <span class="hlt">systems</span> will provide a variety of personal, business, environmental, and industrial digital data services on a global scale. Infosat <span class="hlt">systems</span> provide a niche telecommunications infrastructure that benefit industries and governments of the world whether developing or industrialized; geographically homogeneous or diverse; or low, middle, or high income. The flexible nature of the service allows it to be applied in many ways to meet changing needs. This paper provides an overview of the <span class="hlt">Final</span> Analysis Infosat <span class="hlt">system</span>.</p> <div class="credits"> <p class="dwt_author">Fatig, Michael</p> <p class="dwt_publisher"></p> <p class="publishDate">1997-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">307</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009EGUGA..11..561K"> <span id="translatedtitle">The Late Paleozoic Southern Margin of the Siberian paleocontinent: transformation from an active continental margin to intracontinental <span class="hlt">rifting</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The large volcanoplutonic belt was formed on the southern margin of Siberian paleocontinent in the Early Carboniferous-Early Permian. Now it's stretched through whole Mongolia and the adjacent region of China. In the belt structure there are defined the successive rock complexes: the older one represented by differentiated basalt-andesite-rhyodacite series and younger bimodal complex of basalt-comendite-trachyrhyolite composition. The granodiorite-plagiogranite and diorite-monzonite-granodiorite plutonic massifs are associated with the former, while peralkaline granite massifs are characteristic of the latter. Geochronological results and geological relations between rocks of the bimodal and differentiated complexes showed first that rocks of the differentiated complex originated 350 to 330 Ma ago at the initial stage of forming of the marginal continental belt, linked with development active continental margin. This is evident from geochronological dates obtained for the Adzh-Bogd and Edrengiyn-Nuruu massifs and for volcanic associations of the complex. The dates are consistent with paleontological data. The bimodal association was formed later, 320 to 290 Ma ago. The time span separating formation of two igneous complexes ranges from several to 20-30 m.y. in different areas of the marginal belt. The bimodal magmatism was interrelated with <span class="hlt">rifting</span> responsible for development of the Gobi-Tien Shan <span class="hlt">rift</span> zone in the belt axial part and the Main Mongolian lineament along the belt northern boundary. Loci of bimodal <span class="hlt">rift</span> magmatism likely migrated with time: the respective magmatic activity first initiated on the west of the <span class="hlt">rift</span> <span class="hlt">system</span> and then advanced gradually eastward with development of <span class="hlt">rift</span> structures. Normal granitoids untypical but occurring nevertheless among the products of <span class="hlt">rift</span> magmatism in addition to peralkaline massifs are assumed to have been formed, when the basic magmatism associated with <span class="hlt">rifting</span> stimulated crustal anatexis and generation of crustal granitoid magmas under specific conditions of <span class="hlt">rifting</span> within the active continental margin.</p> <div class="credits"> <p class="dwt_author">Kozlovsky, A. M.; Yarmolyuk, V. V.; Sal'Nikova, E. B.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-04-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">308</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/6750213"> <span id="translatedtitle">Development regimes of <span class="hlt">rifted</span> basins and criteria of their petroleum potential</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The majority of great sedimentary basins were formed primarily by stretching and usually initiated by <span class="hlt">rifting</span>. The evolution and development of intercontinental and passive margin <span class="hlt">rifted</span> basins are discussed. Each basin type described (in the paper) is associated with either single or branched <span class="hlt">rift</span> zones. The basin types are (1) unburied <span class="hlt">rift</span>, i.e., recent <span class="hlt">rifts</span>, or ancient <span class="hlt">rifts</span> with post-<span class="hlt">rift</span> stage without significant subsidence such as East Africa <span class="hlt">rifts</span>, and Reconcavo basin in Brazil; and (2) buried <span class="hlt">rift</span> zones where the post-<span class="hlt">rift</span> stage is characterized by active subsidence and sediment accumulation. The basins often form by repeated <span class="hlt">rifting</span>, and a <span class="hlt">rift</span> zone of a different age may be completely or partially superimposed or separated from other <span class="hlt">rifting</span> events.</p> <div class="credits"> <p class="dwt_author">Larchenkov, E. (Odessa State Univ. (Ukraine))</p> <p class="dwt_publisher"></p> <p class="publishDate">1994-07-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">309</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013EGUGA..1510509P"> <span id="translatedtitle">Influence of the mechanical coupling and inherited strength variations on the geometry of continental <span class="hlt">rifts</span>.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The geometry of continental <span class="hlt">rifts</span> is strongly controlled by the rheology of the lithosphere at the onset of <span class="hlt">rifting</span>. This initial geometry will further control the development of ocean spreading centers and the structure of adjacent passive margins. Therefore, understanding the influence of coupling between the different layers of the lithosphere with and without laterally variable strength in the crust is key when investigating continental <span class="hlt">rifts</span>. In this study we infer the influence of coupling in the crust on the <span class="hlt">rift</span> geometry by means of crustal scale analogue experiments, where we characterize the response of the crust to deformation in terms of the strength ratio between brittle and ductile crust. The degree of coupling has been varied for setups containing or not a pre-existing weak zone. To allow a better description of the geometry obtained in our models, some key observations such as: a) the degree of tilting of the blocks, b) the total width of the graben, c) the displacement along the main fault and d) the distribution of thinning in the lower crust are monitored. Models containing a weak zone are compared to natural examples of the inherited Mozambique Ocean suture zones (MOSZ) in the Red Sea <span class="hlt">rift</span>. The modelling results suggest that deformation is not a-priori localized within pre-existing weak zones unless the coupling between the brittle and the ductile crust is high. With respect to the MOSZ, we infer that: (1) Jurassic NW-SE trending grabens developed parallel to but not within the MOSZ and hence reflect a low degree of coupling whereas (2) Eocene <span class="hlt">rifting</span> in the Red Sea occurred under coupled conditions as deformation strongly focused within the MOSZ. Models without weak zone shows that large-scale detachment faults can also form within a highly coupled crust, which is at variance to the common perception that detachment faulting demands strong decoupling. Our findings shed light on natural <span class="hlt">rift</span> <span class="hlt">systems</span>, which show a wide range of geometries that vary from grabens bounded by high angle normal faults (analogue to the geometry of the Upper Rhine Graben & North Sea Central graben) to listric faults rooting on a basal detachment defining a more asymmetric <span class="hlt">system</span> (similar to the geometry of the golf of Corinth <span class="hlt">rift</span>).</p> <div class="credits"> <p class="dwt_author">Philippon, Melody; van Delft, Pim; van Winden, Matthijs; Zamuroviç, Dejan; Sokoutis, Dimitrios; Willingshofer, Ernst; Cloetingh, Sierd</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-04-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">310</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://eric.ed.gov/?q=%22recommendations+for+occupational%22&id=ED042050"> <span id="translatedtitle">Occupational Training Information <span class="hlt">System</span>. <span class="hlt">Final</span> Report Complete with <span class="hlt">System</span> Documentation.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p class="result-summary">|The overall purpose of the Occupational Training Information <span class="hlt">System</span> (OTIS) is to provide improved data for evaluating recommended changes in Oklahoma's State Plan for Vocational Education. In addition to matching manpower supply and demand to show net demand, the project includes components and cost analysis, a followup, underdeveloped human…</p> <div class="credits"> <p class="dwt_author">Braden, Paul V.; And Others</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">311</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/54539981"> <span id="translatedtitle">Rapid opening along volcanic <span class="hlt">rifted</span> margins: A case of plate-scale elastic deformation and rebound?</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">There is strong evidence from the volcanic <span class="hlt">rifted</span> margins of the North-east Atlantic that <span class="hlt">final</span> rupture (ca. 55.8 Ma) of the continent took place within geologically very short time, perhaps on the order of a few hundred thousand years. Detailed history of igneous productivity as recorded by flood basalts in the Faeroe-East Greenland region and within the seaward-dipping reflector crust</p> <div class="credits"> <p class="dwt_author">H. C. Larsen; C. Hieronymus</p> <p class="dwt_publisher"></p> <p class="publishDate">2003-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">312</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/5705507"> <span id="translatedtitle"><span class="hlt">Final</span> report for TMX-U <span class="hlt">systems</span> support</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">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> <div class="credits"> <p class="dwt_author">Not Available</p> <p class="dwt_publisher"></p> <p class="publishDate">1985-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">313</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/36137320"> <span id="translatedtitle">TFIIH Transcription Factor, a Target for the <span class="hlt">Rift</span> Valley Hemorrhagic Fever Virus</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The <span class="hlt">Rift</span> Valley fever virus (RVFV) is the causative agent of fatal hemorrhagic fever in humans and acute hepatitis in ruminants. We found that infection by RVFV leads to a rapid and drastic suppression of host cellular RNA synthesis that parallels a decrease of the TFIIH transcription factor cellular concentration. Using yeast two hybrid <span class="hlt">system</span>, recombinant technology, and confocal microscopy,</p> <div class="credits"> <p class="dwt_author">Nicolas Le May; Sandy Dubaele; Luca Proietti De Santis; Agnès Billecocq; Michèle Bouloy; Jean-Marc Egly</p> <p class="dwt_publisher"></p> <p class="publishDate">2004-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">314</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2004AGUFM.T12B..06M"> <span id="translatedtitle">Active Normal Fault Behaviour and Continental <span class="hlt">Rift</span> Geometry in the Corinth <span class="hlt">Rift</span>, Greece</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Gulf of Corinth continental <span class="hlt">rift</span>, central Greece extends at up to 15 mm/yr with regular M6+ earthquakes. However, rapid geodetic extension rates in the western <span class="hlt">rift</span> cannot be accounted for by displacement on onshore faults alone, where slip rates determined from uplifted terraces and paleoseismological trenching are significantly lower. High resolution seismic reflection and multibeam bathymetric data were collected to survey offshore faults contributing to extension and quantify their displacement. In the western <span class="hlt">rift</span>, a basement horst on the northern margin is uplifted by the N and S Eratini faults and the axial channel is fault-controlled. Subsided lowstand shorelines in the hangingwall of the N Eratini and the well-studied Aigion fault suggest that both faults have similar displacements. Summed extension from the four major faults across this part of the <span class="hlt">rift</span> (Eliki, Sub-channel, S Eratini, N Eratini) is of the order of 8-12 mm/yr, thereby reconciling geologic and geodetic datasets. Geomorphology indicates that the <span class="hlt">rift</span> geometry changes along axis, with a model of distributed deformation across multiple faults proposed for the western <span class="hlt">rift</span>. The high resolution seismic data linked to sea level history within the gulf (isolated during lowstands) potentially allow changes in slip rate to be determined on a 10000 year timescale. These results compliment the often shorter (100's-10000's years) timescales of onshore fault trenching and uplifted terrace sequences in terms of temporal fault behaviour. Ultimately, seismic hazard can be refined based on fluctuations in past fault behaviour within the <span class="hlt">rift</span>.</p> <div class="credits"> <p class="dwt_author">McNeill, L.; Cotterill, C.; Henstock, T.; Bull, J.; Stefatos, A.; Hicks, S.; Collier, R.; Papatheoderou, G.; Ferentinos, G.</p> <p class="dwt_publisher"></p> <p class="publishDate">2004-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">315</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013SedG..289...40N"> <span id="translatedtitle">Changing physiography of <span class="hlt">rift</span> basins as a control on the evolution of mixed siliciclastic-carbonate back-barrier <span class="hlt">systems</span> (Barremian Iberian Basin, Spain)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">A detailed analysis of both sedimentary facies and stratigraphic architecture of a mixed-siliciclastic carbonate depositional <span class="hlt">system</span> in the synrift Cretaceous Galve sub-basin (eastern Spain), is carried out. Two different stages in the sedimentary evolution are recognised from the stratigraphic architecture of the back-barrier <span class="hlt">system</span>: (1) extensive back-barrier mud flats with tidal creeks, and minor washover fans interbedded with the lagoonal carbonates and influenced by local synsedimentary tectonics (thickness variations, rotated blocks and angular unconformities), and (2) a back-barrier with flat-lying architecture and characterised by washover fan deposits interbedded with lagoonal carbonates, well-developed ebb- and flood-tidal delta deposits and a complete absent of back-barrier tidal mud flats and associated creeks. Evidence suggests that synsedimentary extensional tectonics modified the basin configuration, and tectonically-induced physiographic changes controlled the distribution and areal extension of barrier-island sub-environments (open marine, barrier, and lagoon) and their resultant stratigraphic architecture. Physiographic changes in basin configuration ultimately modulated the effect of tides, which produced changes in depositional sub-environments determining the stacking pattern of depositional <span class="hlt">systems</span>.</p> <div class="credits"> <p class="dwt_author">Navarrete, Rocío; Rodríguez-López, Juan Pedro; Liesa, Carlos L.; Soria, Ana R.; Veloso, Fernanda de Mesquita L.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-05-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">316</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/6572071"> <span id="translatedtitle">Structure of continental <span class="hlt">rifts</span>: Role of older features and magmatism</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Recent geological and geophysical studies in several continental <span class="hlt">rifts</span> have begun to shed light on the details of the processes which govern the structural evolution of these important exploration targets. In Kenya and Tanzania, the classic East African <span class="hlt">rift</span> has been the object of several investigations which reveal that its location follows the boundary (suture ) between the Tanzanian craton (Archean) and Mozambiquan belt (Proterozoic), The Baikal <span class="hlt">rift</span> also follows a similar boundary, and the Mid-continent <span class="hlt">rift</span> of North America appears to do the same. <span class="hlt">Rifts</span> themselves often act as zones of weakness which are reactivated by younger tectonic regimes. The classic North American example of this effect is the Eocambrian Southern Oklahoma aulacogen which was deformed to create the Anadarko basin and Wichita uplift in the late Paleozoic. The Central basin platform has a similar history although the original <span class="hlt">rift</span> formed at [approximately]1,100Ma. Integration of geophysical data with petrologic and geochemical data from several <span class="hlt">rift</span> zones has also provided a new picture of the nature and extent of magmatic modification of the crust. An interesting contradiction is that Phanerozoic <span class="hlt">rifts</span>, except the Afar region, show little evidence for major magmatic modification of the crust whereas, at least in North America, many Precambrian <span class="hlt">rifts</span> are associated with very large mafic bodies in the crust. The Kenya <span class="hlt">rift</span> displays evidence for modification of the lower crust in a two-phase magmatic history, but upper crustal magmatic features are limited to local intrusions associated with volcanoes. In this <span class="hlt">rift</span>, complex basement structure plays a much more important role than previously realized, and the geophysical signatures of basement structure and magmatism are easy to confuse. If this is also the case in other <span class="hlt">rifts</span>, additional <span class="hlt">rift</span> basins remain to be discovered.</p> <div class="credits"> <p class="dwt_author">Keller, G.R. (Univ. of Texas, El Paso, TX (United States))</p> <p class="dwt_publisher"></p> <p class="publishDate">1996-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">317</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009AGUFM.V11F..08G"> <span id="translatedtitle">On the Interaction of a Vigorous Hydrothermal <span class="hlt">System</span> with an Active Magma Chamber: The Puna Magma Chamber, Kilauea East <span class="hlt">Rift</span>, Hawaii</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The extent of the interaction between hydrothermal <span class="hlt">systems</span> and active magma chambers has long been of fundamental interest to the development of ore deposits, cooling of magma chambers, and dehydration of the subducting lithosphere. As volatiles build up in the residual magma in the trailing edge of magmatic solidification fronts, is it possible that volatiles are transferred from the active magma to the hydrothermal <span class="hlt">system</span> and vice versa? Does the external fracture front associated with vigorous hydrothermal <span class="hlt">systems</span> sometimes propagate into the solidification front, facilitating volatile exchange? Or is the magma always sealed at temperatures above some critical level related to rock strength and overpressure? The degree of hydrothermal interaction in igneous <span class="hlt">systems</span> is generally gauged in post mortem studies of ?18O and ?D, where it has been assumed that a fracture front develops about the magma collapsing inward with cooling. H.P. Taylor and D. Norton's (1979; J. Petrol.)seminal work inferred that rocks are sealed with approach to the solidus and there is little to no direct interaction with external volatiles in the active magma. In active lava lakes a fracture front develops in response to thermal contraction of the newly formed rock once the temperature drops to ~950°C (Peck and Kinoshita,1976;USGS PP935A); rainfall driven hydrothermal <span class="hlt">systems</span> flash to steam near the 100 °C isotherm in the solidified lake and have little effect on the cooling history (Peck et al., 1977; AJS). Lava lakes are fully degassed magmas and until the recent discovery of the Puna Magma Chamber (Teplow et al., 2008; AGU) no active magma was known at sufficiently great pressure to contain original volatiles. During the course of routine drilling of an injection well at the Puna Geothermal Venture (PGV) well-field, Big Island, Hawaii, a 75-meter interval of diorite containing brown glass inclusions was penetrated at a depth of 2415 m, continued drilling to 2488 m encountered a melt of dacitic composition of ~67 wt.% SiO2. The melt flowed up the borehole, quenched, and was repeatedly re-drilled over a depth interval of ~8 m, producing several kilograms of clear, colorless vitric cuttings. The melt is of low crystallinity, vesicle-free, at a minimum temperature of ~865°C, and with an apparent viscosity of ~106.5 Pa-s. The magma is separated from the deepest hydrothermal regime at 356°C by 526 m of sealed rock. Heat flux from the magma into the overlying geothermal reservoir at ~2784 mW/m2 is an order of magnitude greater than that for mid-ocean ridges. Typical Hawaiian basalt contains ~0.25 wt.% water. The dacite melt contains ~2.44 wt.% water, and is of normal magmatic ?18O (5.4 ‰) and ?D (-61.8‰), which is in contrast to the surrounding hydrothermal waters. A similar preliminary analysis of the water content in the altered basalt just outside the sealed zone shows it to heavily hydrated (~4.94 wt.%) and altered by the hydrothermal field. This suggests that volatile under-saturated magmas are sealed with respect to hydrothermal fields and deeper <span class="hlt">systems</span> may be even more strongly sealed.</p> <div class="credits"> <p class="dwt_author">Gregory, R. T.; Marsh, B. D.; Teplow, W.; Fournelle, J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">318</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012DokES.442...81Z"> <span id="translatedtitle">Isotopes of hydrogen and oxygen in nitrogen hot springs of Baikal <span class="hlt">Rift</span> Zone in terms of interaction in the water-rock <span class="hlt">system</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The negative correlation between values ?D and ?18O and concentrations of dissolved silicon in nitrogen hot springs is ascertained, which attests to the directed alteration of their hydroisotopic composition towards being depleted in heavy isotopes during interaction in the water-rock <span class="hlt">system</span>. This fact can be allowed for the cases of the lighter isotopic composition of the hot springs of meteogenic origin relative to that of local atmospheric precipitation. The shifts in points of isotopic composition of hot springs from the global meteoric water line can be caused by alterations in either oxygen or hydrogen composition.</p> <div class="credits"> <p class="dwt_author">Zamana, L. V.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">319</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2007AGUFM.T31F..07R"> <span id="translatedtitle">Seismological Investigation of <span class="hlt">Rift</span> Related Uplift: The Rwenzori Network in Western Uganda</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">We present first results from a temporary seismic network located within the western branch of the East-African <span class="hlt">rift</span> <span class="hlt">system</span>. The project aims to constrain the development and uplift of the Rwenzori mountain range and its relation to the formation of the <span class="hlt">rift</span> zone. Local and teleseismic earthquake recordings are used to image structures of the crust and upper mantle within the region. A temporary network consisting of 23 mobile broadband and short-period seismic sensors was operating during a period of about 16 months until October 2007. The stations were located mainly along two profiles in the westernmost part of Uganda near the Congo border. One profile was situated within the <span class="hlt">rift</span> along the eastern flank of the Rwenzori Mountains, approximately between 0.2°S and 0.9°N. The second profile was located nearly perpendicular to the <span class="hlt">rift</span>, extending from the eastern <span class="hlt">rift</span> shoulder into the <span class="hlt">rift</span> valley and further crossing the northern part of the Rwenzori Mountains. Additional seismic stations were placed on the <span class="hlt">rift</span> shoulder in the South-East and the North-West to improve the localization of events. A number of seismological methods are used to study crustal and upper-mantle structure. The localization of sources and fault-plane solutions provide information on active fault zones and on current tectonic movements. Local and teleseismic tomography are applied to determine the 3D velocity structure in the area under investigation and to detect velocity anomalies in the crust and the upper mantle down to approximately 300 km depth. Moho depths are derived from converted phases using receiver functions. Furthermore, shear wave splitting is analyzed to detect regions of anisotropy and their relation to deformation processes and mantle flow. The first analysis of the data shows high seismic activity of the Rwenzori region. Approximately 500 events per month have been located. Focal depths are concentrated between 10 and 20 km. Local P and S-wave tomography using data of the first few months shows significant low velocity anomalies in the northern part of the network, correlated with active volcanic fields and hot springs. From receiver functions, crustal thicknesses of about 23 km have been found beneath the eastern flank of the <span class="hlt">rift</span>. The interpretation of our results will provide constraints for the modeling of geodynamic processes responsible for the formation of the Rwenzori Mountains.</p> <div class="credits"> <p class="dwt_author">Rümpker, G.; Jakovlev, A.; Batte, A.; Lindenfeld, M.; Schumann, A.; Woelbern, I.</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">320</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/6897840"> <span id="translatedtitle">Photovoltaic stand-alone modular <span class="hlt">systems</span>. Phase 2. <span class="hlt">Final</span> Report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The <span class="hlt">final</span> hardware and <span class="hlt">system</span> qualification phase of a two part stand-alone photovoltaic (PV) <span class="hlt">system</span> development is covered. The <span class="hlt">final</span> design incorporated modular, power blocks capable of expanding incrementally from 320 watts to twenty kilowatts (PK). The basic power unit (PU) was nominally rated 1.28 kWp. The controls units, power collection buses and main lugs, electrical protection subsystems, power switching, and load management circuits are housed in a common control enclosure. Photo-voltaic modules are electrically connected in a horizontal daisy-chain method via Amp Solarlok plugs mating with compatible connectors installed on the back side of each photovoltaic module. A pair of channel rails accommodate the mounting of the modules into a frameless panel support structure. Foundations are of a unique planter (tub-like) configuration to allow for world-wide deployment without restriction as to types of soil. One battery string capable of supplying approximately 240 ampere hours nominal of carryover power is specified for each basic power unit. Load prioritization and shedding circuits are included to protect critical loads and selectively shed and defer lower priority or noncritical power demands. The baseline <span class="hlt">system</span>, operating at approximately 2 1/2 PUs (3.2 kW pk.) was installed and deployed. Qualification was successfully complete in March 1983. Since that time, the demonstration <span class="hlt">system</span> has logged approximately 3000 hours of continuous operation under load without major incident.</p> <div class="credits"> <p class="dwt_author">Naff, G.J.; Marshall, N.A.</p> <p class="dwt_publisher"></p> <p class="publishDate">1983-07-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_15");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" 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id="NextPageLink" onclick='return showDiv("page_18");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">321</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3111045"> <span id="translatedtitle">The Pathogenesis of <span class="hlt">Rift</span> Valley Fever</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary"><span class="hlt">Rift</span> Valley fever (RVF) is an emerging zoonotic disease distributed in sub-Saharan African countries and the Arabian Peninsula. The disease is caused by the <span class="hlt">Rift</span> Valley fever virus (RVFV) of the family Bunyaviridae and the genus Phlebovirus. The virus is transmitted by mosquitoes, and virus replication in domestic ruminant results in high rates of mortality and abortion. RVFV infection in humans usually causes a self-limiting, acute and febrile illness; however, a small number of cases progress to neurological disorders, partial or complete blindness, hemorrhagic fever, or thrombosis. This review describes the pathology of RVF in human patients and several animal models, and summarizes the role of viral virulence factors and host factors that affect RVFV pathogenesis.</p> <div class="credits"> <p class="dwt_author">Ikegami, Tetsuro; Makino, Shinji</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">322</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/6529185"> <span id="translatedtitle">Oil exploration in nonmarine <span class="hlt">rift</span> basins of interior Sudan</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">In early 1975 Chevron Overseas Petroleum Inc. commenced a major petroleum exploration effort in previously unexplored interior Sudan. With the complete cooperation of the Sudanese Government, Chevron has acquired a vast amount of geologic and geophysical data during the past 9 years. These data include extensive aeromagnetic and gravity surveys, 25,000 mi (40,200 km) of seismic data, and the results of 66 wells. This information has defined several large <span class="hlt">rift</span> basins which are now recognized as a major part of the Central African <span class="hlt">rift</span> <span class="hlt">system</span>. The sedimentary basins of interior Sudan are characterized by thick Cretaceous and Tertiary nonmarine clastic sequences. Over 35,000 ft (10,600 m) of sediment have been deposited in the deepest trough, and extensive basinal areas are underlain by more than 20,000 ft (6100 m) of sediment. The depositional sequence includes thick lacustrine shales and claystones, flood plain claystones, and lacustrine, fluvial, and alluvial sandstones and conglomerates. Those lacustrine claystones which were deposited in an anoxic environment provide oil-prone source rocks. Reservoir sandstones have been found in a wide variety of nonmarine sandstone facies. The extensional tectonism which formed these basins began in the Early Cretaceous. Movement along major fault trends continued intermittently into the Miocene. This deformation resulted in a complex structural history which led to the formation of several deep fault-bounded troughs, major interbasin high trends, and complex basin flanks. This tectonism has created a wide variety of structures, many of which have become effective hydrocarbon traps.</p> <div class="credits"> <p class="dwt_author">Schull, T.J.</p> <p class="dwt_publisher"></p> <p class="publishDate">1984-04-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">323</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/22924058"> <span id="translatedtitle">An epidemiological model of <span class="hlt">Rift</span> Valley fever with spatial dynamics.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">As a category A agent in the Center for Disease Control bioterrorism list, <span class="hlt">Rift</span> Valley fever (RVF) is considered a major threat to the United States (USA). Should the pathogen be intentionally or unintentionally introduced to the continental USA, there is tremendous potential for economic damages due to loss of livestock, trade restrictions, and subsequent food supply chain disruptions. We have incorporated the effects of space into a mathematical model of RVF in order to study the dynamics of the pathogen spread as affected by the movement of humans, livestock, and mosquitoes. The model accounts for the horizontal transmission of <span class="hlt">Rift</span> Valley fever virus (RVFV) between two mosquito and one livestock species, and mother-to-offspring transmission of virus in one of the mosquito species. Space effects are introduced by dividing geographic space into smaller patches and considering the patch-to-patch movement of species. For each patch, a <span class="hlt">system</span> of ordinary differential equations models fractions of populations susceptible to, incubating, infectious with, or immune to RVFV. The main contribution of this work is a methodology for analyzing the likelihood of pathogen establishment should an introduction occur into an area devoid of RVF. Examples are provided for general and specific cases to illustrate the methodology. PMID:22924058</p> <div class="credits"> <p class="dwt_author">Niu, Tianchan; Gaff, Holly D; Papelis, Yiannis E; Hartley, David M</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-08-13</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">324</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/34794064"> <span id="translatedtitle">Experimental <span class="hlt">Rift</span> Valley fever in rhesus macaques</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Summary <span class="hlt">Rift</span> Valley fever (RVF) is a major cause of human morbidity and mortality in endemic areas of sub-Saharan Africa and has the potential to cause epidemic disease in receptive areas world-wide. In this study, a RVF viral isolate from the 1977 Egyptian epidemic (ZH-501) inoculated intravenously into rhesus macaques caused a benign viremic infection in most, but resulted in</p> <div class="credits"> <p class="dwt_author">C. J. Peters; D. Jones; R. Trotter; J. Donaldson; J. White; E. Stephen; T. W. Slone</p> <p class="dwt_publisher"></p> <p class="publishDate">1988-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">325</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.geo.tu-freiberg.de/oberseminar/os06_07/helbig.pdf"> <span id="translatedtitle">Oblique <span class="hlt">Rifting</span> on Reykjanes Peninsula, SW Iceland</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Reykjanes Peninsula offers the only on-shore outcrop of an currently active, oblique spreading zone of the Mid-Atlantic Ridge and thus, it is an excellent natural laboratory to investigate the structural geometries and the evolution of oblique <span class="hlt">rift</span> zones. The Reykjanes Peninsula is characterised by dinstinct regions of (1) seismic activity along the current spreading axis and (2) discrete en-échelon fracture</p> <div class="credits"> <p class="dwt_author">Maria Helbig</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">326</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/6535806"> <span id="translatedtitle">Early Paleozoic sedimentation in Reelfoot <span class="hlt">rift</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Analysis of subsurface data from deep tests drilled in the northern Mississippi embayment and southern Mid-Continent suggests that earliest Paleozoic sedimentation was dominated by the tectonic evolution of the Reelfoot <span class="hlt">rift</span>. Throughout most of the Mid-Continent, the Upper Cambrian Lamotte (Mt. Simon) sandstone rests nonconformably on Precambrian basement and is overlain by the Bonneterre (Eau Claire) Formation. However, in the area of the Reelfoot <span class="hlt">rift</span>, both the Lamotte and Bonneterre grade into thick, basinal shales that locally display evidence of episodic deposition of coarse clastics, perhaps on submarine fans. Moreover, two major sedimentary units are present beneath the Lamotte-Bonneterre basinal facies within the Reelfoot <span class="hlt">rift</span>. Immediately underlying the Lamotte-Bonneterre shale is a carbonate stratum (probably dolomite) that thickens to more than 1,000 ft (300 m) along the axis of the basin in eastern Arkansas. Underlying this carbonate is a detrital unit that grades from arkosic sandstone near the northern terminus of the basin to a basinal shale southward. This basinal shale is at least several hundred feet thick near the axis of the basin. These two strata occupy the stratigraphic position of the Conasauga (Middle Cambrian) and Rome (Lower Cambrian) Formations of the southern Appalachians. The axial and transverse distribution of these strata suggests that the Reelfoot evolved as paired grabens or half grabens during the Early and Middle Cambrian. Subsequently, the Reelfoot remained the axis for more widespread subsidence and sedimentation throughout much of the Paleozoic.</p> <div class="credits"> <p class="dwt_author">Houseknecht, D.W.; Weaverling, P.H.</p> <p class="dwt_publisher"></p> <p class="publishDate">1983-09-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">327</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/61289586"> <span id="translatedtitle">MidContinent <span class="hlt">rift</span>: new frontier in an old area</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The Mid-Continent <span class="hlt">rift</span> (MCR) is a 2000-km-long intracontinental feature of middle Proterozoic age (1.1 Ga) that extends from Kansas northeastward through the Lake Superior basin and then southeastward through the lower peninsula of Michigan. The authors believe that <span class="hlt">rift</span>-related marginal basins overlying axial basins and other structures associated with this feature may locally be prospective within four geographically identifiable <span class="hlt">rift</span></p> <div class="credits"> <p class="dwt_author">D. M. Jr. Davidson; M. G. Jr. Mudrey</p> <p class="dwt_publisher"></p> <p class="publishDate">1986-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">328</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/6948448"> <span id="translatedtitle">Advanced power conditioning for maglev <span class="hlt">systems</span>. <span class="hlt">Final</span> report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The <span class="hlt">final</span> report contains parametric scaling data and computer models of power conditioning equipment applicable to the design of an advanced maglev <span class="hlt">system</span>. The power conditioning topologies were selected based on data from a literature search, on characteristics of present power semiconductor technology devices, and on actual performance characterization of designs using a circuit analysis program. The analyses show that GTOs are the best switches for traction drives, input power conditioning equipment, and the braking chopper. At lower power levels, as required for auxiliary power and superconducting coil power conditioning, the IGBT appeared to be the best switch.</p> <div class="credits"> <p class="dwt_author">Nerem, A.; Bowles, E.E.; Chapelle, S.; Callanan, R.J.</p> <p class="dwt_publisher"></p> <p class="publishDate">1992-08-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">329</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2005AGUFM.T13C0485J"> <span id="translatedtitle">Geodynamic Evolution of the Southern Flank of the Corinth <span class="hlt">Rift</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Gulf of Corinth is the most seismically active area of Europe extending in a N-S direction at a rate of 12mm/yr. Many studies have focused on currently active normal faults, which bound the southern flank of the Corinth <span class="hlt">rift</span>. However, many prominent faults, that are considered no longer active, outcrop over a broader area along with their syn-<span class="hlt">rift</span> sedimentary sequence. The normal fault network and related synrift succession have been mapped and studied at a scale of 1:25,000. The geometry of the fault network in 3D has been reconstructed in the gOcad 3D geomodelling package. Based on these detailed field data we propose a geodynamic model for the evolution of the region in three steps over the last two million years. From 2 to 1 Ma, extension affected a broad area at least twenty kilometers wide. Alluvial conglomerates and sandstones, deposited in grabens and half grabens, were derived from erosion of the pre-existing (Hellenic) high relief to the south in the Peloponnese massif. Around 1Ma, a regional uplift led to the migration of the depocenter to the north. New faults are activated closer to the coast, in places generating forced folds that tilted synrift fluvial formations northward over a 2-3 kilometers wide area. Considerable accommodation space was generated by these faults and, with an increased sediment supply from the south, a series of giant marine Gilbert deltas developed in their hangingwalls. <span class="hlt">Finally</span>, from 0.5 Ma to present, the activation of a series of major new faults further to the north (near the current coastline) coincided with regional uplift of the south coastal belt, and initiated the formation of a second generation of Gilbert delta, currently building out into the gulf. The faults can be divided into three families. The main one (74 data) is oriented N110, dipping 45 to 60° to the north. It includes 5 major faults spaced 3 to 5 km from south to north, with a throw larger than 1000m. A secondary set (41 data) strikes N60, dipping to the NW, it includes only one fault with a throw larger than 500m; the other secondary set (43 data) is antithetic to the two first ones as it strikes N60 to N110, dipping to the south, the largest fault it includes has a throw of about 400m. Most faults are planar and the importance of listric faults seems minor in the <span class="hlt">rift</span> history.</p> <div class="credits"> <p class="dwt_author">Jousselin, D.; Bourlange, S.; Ford, M.; Le Carlier, C.; Rohais, S.</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">330</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/5550438"> <span id="translatedtitle">Physical characteristics and evolutionary trends of continental <span class="hlt">rifts</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary"><span class="hlt">Rifts</span> may be defined as zones beneath which the entire lithosphere has ruptured in extension. They are widespread and occur in a variety of tectonic settings, and range up to 2,600 m.y. in age. The object of this review is to highlight characteristic features of modern and ancient <span class="hlt">rifts</span>, to emphasize differences and similarities in order to help characterize evolutionary trends, to identify physical conditions favorable for initiation as well as termination of <span class="hlt">rifting</span>, and to provide constraints for future modeling studies of <span class="hlt">rifting</span>. <span class="hlt">Rifts</span> are characterized on the basis of their structural, geomorphic, magmatic and geophysical features and the diverse character of these features and their evolutionary trends through time are discussed. Mechanisms of <span class="hlt">rifting</span> are critically examined in terms of the physical characteristics and evolutionary trends of <span class="hlt">rifts</span>, and it is concluded that while simple models can give valuable insight into specific processes of <span class="hlt">rifting</span>, individual <span class="hlt">rifts</span> can rarely, if ever, be characterized by well defined trends predicted by these models. More data are required to clearly define evolutionary trends, and the models require development to incorporate the effects of lithospheric heterogeneities and complex geologic histories.</p> <div class="credits"> <p class="dwt_author">Ramberg, I.B.; Morgan, P.</p> <p class="dwt_publisher"></p> <p class="publishDate">1984-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">331</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2001AGUFM.T51B0869D"> <span id="translatedtitle">Current Magmato-Tectonic Activity in the Asal-Ghoubbet <span class="hlt">Rift</span> (Afar Depression, Republic of Djibouti)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Asal-Ghoubbet <span class="hlt">rift</span>, the most active, emerged segment of the Aden ridge, opens at 16+/-2 mm/yr. Although normal faulting operates in the <span class="hlt">rift</span>, it does not accommodate the entire extension, so that dyking must occur at depth. In order to investigate the current relationship between tectonics and magmatism, we installed 11 seismometers (3 3C + one broad band; plus 6 permanent stations) in the northeastern part of the <span class="hlt">rift</span>, site of the most active faults and of the Fieale volcano caldera, and monitored the seismic activity during 5 months. About 200 small-magnitude (time, <= 3) events could be accurately ( ~ 300m) localized in the emerged part of the <span class="hlt">rift</span>, using an appropriate velocity model. All fall within the temporary network, forming three major clusters. Nine % of the events spread in the outermost part of the <span class="hlt">rift</span> northern shoulder, where clear active faults and volcanic structures are lacking. All seem to nucleate at a similar depth, of 6-8 km. Seven % of the events nucleate at a shallow depth ( ~1 km) in the northern Disa Le Mallo subrift, zone of intense active faulting and fissuring. <span class="hlt">Finally</span>, the majority of events (70%) cluster below the Fieale caldera, at a mean depth of 3 km, hence just above the inferred magma chamber. The analysis of the broader-scale seismological data acquired in the <span class="hlt">rift</span> over the last 20 years, points to a similar distribution. Thirty five out of 50 focal mechanisms we calculated using P wave polarities, are consistent with a double-couple source model, and reveal predominant normal faulting on NW-SE-striking planes parallel to the faults which structure the <span class="hlt">rift</span>. Fifteen events, however, show non-double couple radiation pattern, particularly in the Fieale area. These particular events may result from magmatic activity (filling or collapse of the magma chamber) and/or geothermal processes. In the other two areas, where they are also found, their origin is possibly related to fissuring or dyking. One seismic sequence also occurred, with 48 events in 10 days below the Fieale caldera, and seismic quiescence everywhere else. The focal mechanisms determined for 19 of these events exhibit double-couple patterns, with nodal planes (normal faulting) having strikes roughly parallel to the caldera rings. The sequence may attest to ring faulting, perhaps related to collapse of the caldera floor in connection with magmatism. Such preliminary results imply that seismicity in the <span class="hlt">rift</span> results from both tectonic deformation and magmatism in the crust. However, although active faults extend 40 km from Lake Asal (NW) to the Ghoubbet (SE), only those in the northeastern, emerged part of the <span class="hlt">rift</span> appear to be seismic in the last 20 years. Similarly, although the last (1978) volcanic event occurred at the northwestern tip of the <span class="hlt">rift</span>, only the Fieale caldera, to the SE, is a site of present seismicity.</p> <div class="credits"> <p class="dwt_author">Doubre, C.; Doubre, C.; Dorbath, L.; Manighetti, I.; Jacques, E.; Geoffroy, L.</p> <p class="dwt_publisher"></p> <p class="publishDate">2001-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">332</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2007AGUSM.S31A..02L"> <span id="translatedtitle">Variable styles of <span class="hlt">rifting</span> expressed in crustal structure across three <span class="hlt">rift</span> segments of the Gulf of California</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">We present a summary of results from a crustal-scale seismic experiment conducted in the southern Gulf of California. This experiment, the PESCADOR experiment, imaged crustal structure across three <span class="hlt">rift</span> segments, the Alarcon, Guaymas, and San José del Cabo to Puerto Vallarta (Cabo-PV) segments, using seismic refraction/wide-angle reflection data acquired with airgun sources and recorded by closely spaced (10-15 km) ocean-bottom seismometers (OBSs). The imaged crustal structure reveals a surprisingly large variation in <span class="hlt">rifting</span> style and magmatism between these segments: the Alarcon segment is a wide <span class="hlt">rift</span> with apparently little syn-<span class="hlt">rift</span> magmatism; the Guaymas segment is a narrow, magmatically robust <span class="hlt">rift</span>; and the Cabo-PV segment is a narrow, magmatically "normal" <span class="hlt">rift</span>. Our explanation for the observed variability is non-traditional in that we do not invoke mantle temperature, the factor commonly invoked to explain end-member volcanic and non-volcanic <span class="hlt">rifted</span> margins, as the source of the considerable, though non-end-member variability we observe. Instead, we invoke mantle depletion related to pre-<span class="hlt">rift</span> arc volcanism to account for observed wide, magma-poor <span class="hlt">rifting</span> and mantle fertility and possibly the influence of sediments to account for robust <span class="hlt">rift</span> and post-<span class="hlt">rift</span> magmatism. These factors may commonly vary over small lateral spatial scales in regions that have transitioned from convergent to extensional tectonics, as is the case for the Gulf of California and many other <span class="hlt">rifts</span>. Our hypothesis suggests that substantial lateral variability may exist within the uppermost mantle beneath the Gulf of California today, and it is hoped that ongoing efforts to image upper mantle structure here will provide tests for this hypothesis.</p> <div class="credits"> <p class="dwt_author">Lizarralde, D. D.; Axen, G. J.; Brown, H. E.; Fletcher, J. M.; Fernandez, A. G.; Harding, A. J.; Holbrook, W. S.; Kent, G. M.; Paramo, P.; Sutherland, F. H.; Umhoefer, P. J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-05-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">333</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ntis.gov/search/product.aspx?ABBR=ADA478110"> <span id="translatedtitle">Rapidly Installed Fluid Transfer <span class="hlt">System</span> (<span class="hlt">RIFTS</span>).</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ntis.gov/search/index.aspx">National Technical Information Service (NTIS)</a></p> <p class="result-summary">Fossil fuels will continue to be the primary propulsion fuel for military aircraft, vehicles, and ground equipment for the foreseeable future. Water is the critical fuel to sustain the ultimate weapon, our soldiers. Distributing large quantities of bulk f...</p> <div class="credits"> <p class="dwt_author">R. Li</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">334</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/42010039"> <span id="translatedtitle"><span class="hlt">Rifting</span> and lower crustal reflectivity: A case study of the intracratonic Dniepr-Donets <span class="hlt">rift</span> zone, Ukraine</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Intracratonic <span class="hlt">rifting</span>, caused by late Devonian extensional stresses in\\u000a the East European Craton, created the largest <span class="hlt">rift</span> zone in Europe, the\\u000a Pripyat-Dniepr-Donets <span class="hlt">rift</span> (southeast Ukraine). The <span class="hlt">rift</span> basin is\\u000a approximately 2000 km long, up to 170 km wide, and 22 km deep.\\u000a Wide-angle refraction and reflection seismic data from the Donbas Basin\\u000a deep seismic Refraction and Reflection Experiments (DOBRE' 99)</p> <div class="credits"> <p class="dwt_author">Stig B. Lyngsie; Hans Thybo; Rasmus Lang</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">335</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013EGUGA..15.6969J"> <span id="translatedtitle">Non-cylindricity of mountain belts: a case for rheological and <span class="hlt">rift</span> inheritance</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Many mountain belts exhibit significant along strike variation in structural style with changes in the width of the orogen, the thickness of thick-skinned thrust sheets, the geometry and kinematics of the crustal-scale thrust <span class="hlt">system</span>, and the degree of partitioning between pro- and retro-wedge deformation. While the main factors controlling structural style are understood to first order the cause of these lateral variations remains to be resolved. Here we focus on the Pyrenean example that is characterized by significant lateral variation in structural style with an antiformal stack in the eastern section and thick-skinned deformation in its western part. The Mesozoic <span class="hlt">rifting</span> event preceding Pyrenean mountain building was similarly characterized by significant lateral variation in structure, with wide distributed extension in the eastern segment and very narrow <span class="hlt">rifting</span> in its western part leading to mantle exhumation. We integrate the available geological and geophysical data with forward numerical models of both the <span class="hlt">rifting</span> event and lithosphere scale inversion leading to mountain building. We show that a lateral variation in crustal strength related to inherited Variscan crustal composition explains both the variation in structural style during Mesozoic <span class="hlt">rifting</span> as well as those observed during Pyrenean mountain building.</p> <div class="credits"> <p class="dwt_author">Jammes, Suzon; Huismans, Ritske S.; Muñoz, Josep Anton</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-04-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">336</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/41994481"> <span id="translatedtitle">Magma chambers modeled as cavities explain the formation of <span class="hlt">rift</span> zone central volcanoes and their eruption and intrusion statistics</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The volcanic <span class="hlt">rift</span> zone in Iceland is characterized by elongate volcanic <span class="hlt">systems</span>, consisting of tension fractures, normal faults and volcanic fissures, where most of the volcanotectonic activity takes place. Most volcanic <span class="hlt">systems</span> develop central volcanoes, the formation of which is still poorly understood. There is great difference in the eruption and intrusion statistics of the volcanic <span class="hlt">systems</span> inside and outside</p> <div class="credits"> <p class="dwt_author">Agust Gudmundsson</p> <p class="dwt_publisher"></p> <p class="publishDate">1998-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">337</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.agu.org/journals/jb/v103/iB04/97JB03747/97JB03747.pdf"> <span id="translatedtitle">Magma chambers modeled as cavities explain the formation of <span class="hlt">rift</span> zone central volcanoes and their eruption and</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The volcanic <span class="hlt">rift</span> zone in Iceland is characterized by elongate volcanic <span class="hlt">systems</span>, consisting of tension fractures, normal faults and volcanic fissures, where most of the volcanotectonic activity takes place. Most volcanic <span class="hlt">systems</span> develop central volcanoes, the formation of which is still poorly understood. There is great difference in the eruption and intrusion statistics of the volcanic <span class="hlt">systems</span> inside and outside</p> <div class="credits"> <p class="dwt_author">Agust Gudmundsson</p> <p class="dwt_publisher"></p> <p class="publishDate">1998-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">338</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/5851345"> <span id="translatedtitle">Expanded bicycling route <span class="hlt">system</span> for Denver. <span class="hlt">Final</span> technical report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">This <span class="hlt">final</span> report describes the results of a study of the potential energy savings associated with increased utilitarian bicycle transportation in the Denver metropolitan area. The project has included computer modeling of the carrying capacity of the present bicycle route <span class="hlt">system</span>, future route <span class="hlt">systems</span>, as well as outreach activities to convey the results to public officials and the general public. A key feature of the project has been a consideration of the benefits associated with an expanded bikeway <span class="hlt">system</span> which includes ''bike boulevards''. Data from the west coast cities and other sources, have been used to generate quantitative estimates of the benefits associated with a Denver bikeway <span class="hlt">system</span> which includes bike boulevards. The development of a network of bike boulevards in Denver should result in energy savings of about 20.2 million gallons of gasoline per year, as well as a 3.4% reduction in vehicular carbon monoxide emissions. These benefits are in addition to those accruing from current levels of bicycling.</p> <div class="credits"> <p class="dwt_author">Maltempo, M.M.</p> <p class="dwt_publisher"></p> <p class="publishDate">1983-11-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">339</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/5934965"> <span id="translatedtitle"><span class="hlt">Rift</span> basin evolution and the growth of normal faults</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The three-dimensional displacement geometry associated with micro-normal faults in sedimentary strata closely resembles the pattern of subsidence and uplift following earthquakes on parts of normal fault <span class="hlt">systems</span>. Both are similar to the large-scale geometry of half-graben sedimentary basins and their uplifted footwall blocks. These observations suggest that (1) half-graben evolve as a consequence of repeated slip events on basin-bounding normal faults and (2) normal fault <span class="hlt">systems</span> grow in length through time as displacement accumulates. Furthermore, details of the evolution of basins and their border fault <span class="hlt">systems</span> (BFS) should be recorded in the basin fill. Indeed, Triassic synrift strata progressively onlap basement along the margins of many eastern North American <span class="hlt">rift</span> basins, implying that these basins grew in length and width. A progressive decrease in accumulation rates through the Triassic section is also consistent with basin growth. Forward modeling involving basin growth, however, indicates that both features need not always occur. On the largest scale, a typical Mesozoic <span class="hlt">rift</span> basin approximates a large syncline plunging toward its associated BFS. This geometry suggests that cumulative fault displacement and associated basin subsidence were highest near the center of the map trace of the BFS. On a smaller scale, transverse growth folds in the hanging wall of the BFS are associated with a segmentation of the BFS: synclines formed where fault segment displacement was highest; anticlines formed where displacement was lower, generally at the boundaries of fault segments. Thus, along-strike variations in fault displacement occur on a variety of scales. In addition, the map trace of the basement-sediment contact is apparently unaffected by the transverse folds and the segmentation of the BFS, implying some form of regional linkage among the segments of the BFs and perhaps other faults within the basin.</p> <div class="credits"> <p class="dwt_author">Schlische, R.W. (Rutgers, The State Univ. of New Jersey, Piscataway, NJ (United States). Dept. of Geological Sciences)</p> <p class="dwt_publisher"></p> <p class="publishDate">1992-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">340</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2003AGUFM.S52G..05S"> <span id="translatedtitle">Understanding the Transition From Continental to Oceanic <span class="hlt">Rifting</span> in the Northern Ethiopian <span class="hlt">Rift</span> - the EAGLE Project</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">A consortium of UK (Leeds, Leicester, Royal Holloway, Edinburgh,), US (Stanford, UTEP, Penn State,) and Ethiopian (Addis Ababa) universities are exploring the kinematics and dynamics of continental breakup through the Ethiopia Afar Geoscientific Lithospheric Experiment (EAGLE), which aims to probe the crust and upper mantle structure between the Main Ethiopian (continental) and Afar (ocean spreading) <span class="hlt">rifts</span>. EAGLE is a multi-disciplinary study centered around a set of passive and controlled-source seismic experiments, and incorporates additional magnetotelluric, gravity, GPS and petrological studies. The initial Phase I seismic experiment consisted of a deployment of 30 broadband seismometers for a period of 16 months (Oct. 2001 to Jan. 2003) over a 250 km x 250 km area of the <span class="hlt">rift</span> valley and its uplifted flanks. P- and S-wave tompography from teleseismic traveltime residuals, SKS splitting analyses and receiver functions provide images of crust and deep earth structure. The Phase II seismic experiment consisted of a further 50 broadband instruments for a period of 4 months over a 200 km x 100 km area encompassing 4 magmatic segments in the Main Ethiopian <span class="hlt">Rift</span>. These recordings have furthered our understanding of the location of active seismicity, fault plane mechanisms and segmentation of <span class="hlt">rift</span> crustal structure. Phase III consisted of the deployment of a further 1100 seismic instruments during a controlled source seismic project involving 20 shots being fired into one 450 km cross-<span class="hlt">rift</span> profile (Profile 1), one 450 km axial profile (Profile 2), and a dense 2D array of instruments in a 150 km diameter circle around the profiles1 intersection (Profile 3), all centered on the magmatically active Nazret region. The crust and upper mantle velocity models derived provide estimates of total crustal thinning across the <span class="hlt">rift</span>, assess the role of basement in the location of major faults and magmatic segments, and determine whether significant underplating takes place. An 18 sounding magnetotelluric profile along the cross <span class="hlt">rift</span> profile I provides additional constraints on the nature and distribution of crustal heterogeneity, and images melt accumulation zones. New gravity and geodetic information have also been acquired.</p> <div class="credits"> <p class="dwt_author">Stuart, G.</p> <p class="dwt_publisher"></p> <p class="publishDate">2003-12-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_16");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' 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src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">341</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/993614"> <span id="translatedtitle">Practical reliability and uncertainty quantification in complex <span class="hlt">systems</span> : <span class="hlt">final</span> report.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">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 minimize the risk of making a wrong decision about the fitness of a <span class="hlt">system</span>. We conclude this report by proposing additional fruitful areas of research.</p> <div class="credits"> <p class="dwt_author">Grace, Matthew D.; Ringland, James T.; Marzouk, Youssef M. (Massachusetts Institute of Technology, Cambridge, MA); Boggs, Paul T.; Zurn, Rena M.; Diegert, Kathleen V. (Sandia National Laboratories, Albuquerque, NM); Pebay, Philippe Pierre; Red-Horse, John Robert (Sandia National Laboratories, Albuquerque, NM)</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-09-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">342</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2004AGUFM.T14A..06W"> <span id="translatedtitle">Neotectonic Structure of Terror <span class="hlt">Rift</span>, Western Ross Sea, Antarctica: Initial Interpretations of New Geophysical Data</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Terror <span class="hlt">Rift</span> in the western Ross Sea is a prominent neotectonic element of the West Antarctic <span class="hlt">Rift</span>, yet insufficient data have been available to define the geometries of faults and volcanic bodies or to constrain <span class="hlt">rift</span> timing in any detail. The RVIB Nathaniel B. Palmer completed a geophysical cruise in the western Ross Sea in early 2004 in order to better understand the history and kinematics of the Terror <span class="hlt">Rift</span>. Over 7000 km of gravity, magnetic and multibeam bathymetric data were obtained, and extensive new multichannel (2000 km) and single-channel (500 km) seismic reflection profiles were acquired. In addition to the geophysical data, dredging and sampling of submarine and exposed volcanic vents were completed. Limited access to the westernmost Ross Sea due to extensive ice cover precluded complete profiling across the Terror <span class="hlt">Rift</span>. A significant improvement in line spacing over the eastern Terror <span class="hlt">Rift</span>, however, allows us to define the eastern limit of the <span class="hlt">rift</span> basin, and to map fault geometries, displacements and along strike variations in border and intrabasinal fault <span class="hlt">systems</span>. Volcanic features were mapped by both bathymetric and geophysical data. New mapping of the volcanic field surrounding Franklin Island revealed clusters of submarine volcanic cones and connecting volcanic ridges. The field as a whole has a north to northeast elongation. A separate series of prominent volcanic edifices define a NNW trend extending northward from Beaufort Island and is associated with a zone of intense faulting. Another large submarine volcanic complex is located east of Beaufort Island. In McMurdo Sound, volcanic ridges radiate from the western margin of Ross Island. Successful dredging of seven submarine cones yielded basaltic rocks containing abundant glassy material, as well as mantle and crustal xenoliths. Faults were imaged in the western part of McMurdo Sound and prominent unconformities related to downward flexure in response to Ross Island volcano mass loads were imaged in the eastern Sound. These new seismic profiles will allow us to derive a regional flexural history for this part of the basin. Intriguing glacial erosional and depositional features were clearly imaged by the bathymetric data and provide us with a means to constrain relative timing of glaciation, volcanism and tectonism in the region.</p> <div class="credits"> <p class="dwt_author">Wilson, T. J.; Lawver, L. A.; Henrys, S.</p> <p class="dwt_publisher"></p> <p class="publishDate">2004-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">343</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.cdc.gov/ncidod/eid/vol4no2/adobe/fon.pdf"> <span id="translatedtitle">New Vectors of <span class="hlt">Rift</span> Valley Fever in West Africa</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">After an outbreak of <span class="hlt">Rift</span> Valley fever in Southern Mauritania in 1987, entomologic studies were conducted in a bordering region in Sénégal from 1991 to 1996 to identify the sylvatic vectors of <span class="hlt">Rift</span> Valley fever virus. The virus was isolated from the floodwater mosquitoes Aedes vexans and Ae. ochraceus. In 1974 and 1983, the virus had been isolated from Ae.</p> <div class="credits"> <p class="dwt_author">D. Fontenille; M. Traore-Lamizana; M. Diallo; J. Thonnon; J. P. Digoutte; H. G. Zeller</p> <p class="dwt_publisher"></p> <p class="publishDate">1998-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">344</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2008AGUFM.G21A0678S"> <span id="translatedtitle">Strain distribution in the East African <span class="hlt">Rift</span> from GPS measurements</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary"><span class="hlt">Rifting</span> of continental lithosphere is a fundamental process that controls the growth and evolution of continents and the birth of ocean basins. Most <span class="hlt">rifting</span> models assume that stretching results from far-field lithospheric stresses from plate motions, but there is evidence that asthenospheric processes play an active role in <span class="hlt">rifting</span>, possibly through viscous coupling and/or the added buoyancy and thermal weakening from melt intrusions. The distribution of strain during <span class="hlt">rifting</span> is a key observable to constrain such models but is however poorly known. The East African <span class="hlt">Rift</span> (EAR) offers a unique opportunity to quantify strain distribution along and across an active continental <span class="hlt">rift</span> and to compare a volcanic (Eastern branch) and a non-volcanic (Western branch) segment. In 2006, we established and first surveyed a network of 35 points across Tanzania and installed one continuous station in Dar Es Salaam (TANZ), followed in 2008 by a second occupation campaign. We present a preliminary velocity field for the central part of the EAR, spanning both the Western and Eastern <span class="hlt">rift</span> branches. We compare our results with a recent kinematic model of the EAR (Stamps et al., GRL, 2008) and discuss its significance for understanding <span class="hlt">rifting</span> processes.</p> <div class="credits"> <p class="dwt_author">Stamps, S. D.; Saria, E.; Calais, E.; Delvaux, D.; Ebinger, C.; Combrinck, L.</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">345</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/55212108"> <span id="translatedtitle">Rio Grande <span class="hlt">Rift</span> GPS Measurements 2006-2009</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">We use three years of measurements from 25 continuous GPS stations across the Rio Grande <span class="hlt">Rift</span> in New Mexico and Colorado to estimate surface velocities, time series, baselines, and strain rates. The stations are part of the EarthScope Rio Grande <span class="hlt">Rift</span> experiment, a collaboration between researchers at the University of Colorado at Boulder, the University of New Mexico, and Utah</p> <div class="credits"> <p class="dwt_author">H. Berglund; A. F. Sheehan; R. Nerem; J. Choe; A. R. Lowry; M. Roy; F. Blume; M. Murray</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">346</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3358149"> <span id="translatedtitle">Prevalence of <span class="hlt">Rift</span> Valley Fever among Ruminants, Mayotte</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary"><span class="hlt">Rift</span> Valley fever threatens human and animal health. After a human case was confirmed in Comoros in 2007, 4 serosurveys among ruminants in Mayotte suggested that <span class="hlt">Rift</span> Valley fever virus had been circulating at low levels since 2004, although no clinical cases occurred in animals. Entomologic and ecologic studies will help determine outbreak potential.</p> <div class="credits"> <p class="dwt_author">Pedarrieu, Aurelie; Guis, Helene; Defernez, Cedric; Bouloy, Michele; Favre, Jacques; Girard, Sebastien; Cardinale, Eric; Albina, Emmanuel</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">347</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pmc.ucsc.edu/~fnimmo/website/paper28.pdf"> <span id="translatedtitle">Dynamics of <span class="hlt">rifting</span> and modes of extension on icy satellites</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">A simple numerical model of extension in icy satellite shells is developed. Thinning of the ice weakens the shell, promoting further extension. If lateral flow in the lower part of the shell is unimportant, extension is opposed and wide <span class="hlt">rifts</span> are generated; if lateral flow is rapid, localized extension is favored and narrow <span class="hlt">rifts</span> are produced. Thick shells or high</p> <div class="credits"> <p class="dwt_author">F. Nimmo</p> <p class="dwt_publisher"></p> <p class="publishDate">2004-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">348</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ntis.gov/search/product.aspx?ABBR=N7824024"> <span id="translatedtitle">Martian Canyons and African <span class="hlt">Rifts</span>: Structural Comparisons and Implications.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ntis.gov/search/index.aspx">National Technical Information Service (NTIS)</a></p> <p class="result-summary">The resistant parts of the canyon walls of the Martian <span class="hlt">rift</span> complex Valled Marineris were used to infer an earlier, less eroded reconstruction of the major roughs. The individual canyons were then compared with individual <span class="hlt">rifts</span> of East Africa. When measur...</p> <div class="credits"> <p class="dwt_author">H. Frey</p> <p class="dwt_publisher"></p> <p class="publishDate">1978-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">349</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/55039116"> <span id="translatedtitle">Present-day Kinematics of the East African <span class="hlt">Rift</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The East African <span class="hlt">Rift</span> (EAR), a ~5000 km-long series of seismically active structures that mark the divergent boundary between the Somalia and Nubia plates, is often cited as a modern archetype for <span class="hlt">rifting</span> and continental breakup. Paradoxically, its current kinematics is the least well-known of all major plate boundaries, owing to its tremendous extent, difficult access, and lack of geodetic</p> <div class="credits"> <p class="dwt_author">D. S. Stamps; E. Calais; E. Saria; E. Mbede; C. Ebinger; D. Delvaux; F. Kervyn; L. Combrinck; C. Hartnady; J. Nocquet; R. Fernandes</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">350</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/22607651"> <span id="translatedtitle">Prevalence of <span class="hlt">Rift</span> Valley Fever among ruminants, Mayotte.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary"><span class="hlt">Rift</span> Valley fever threatens human and animal health. After a human case was confirmed in Comoros in 2007, 4 serosurveys among ruminants in Mayotte suggested that <span class="hlt">Rift</span> Valley fever virus had been circulating at low levels since 2004, although no clinical cases occurred in animals. Entomologic and ecologic studies will help determine outbreak potential. PMID:22607651</p> <div class="credits"> <p class="dwt_author">Cêtre-Sossah, Catherine; Pédarrieu, Aurélie; Guis, Hélène; Defernez, Cédric; Bouloy, Michèle; Favre, Jacques; Girard, Sébastien; Cardinale, Eric; Albina, Emmanuel</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-06-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">351</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/22608405"> <span id="translatedtitle">Genome analysis of <span class="hlt">Rift</span> Valley fever virus, Mayotte.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">As further confirmation of a first human case of <span class="hlt">Rift</span> Valley fever in 2007 in Comoros, we isolated <span class="hlt">Rift</span> Valley fever virus in suspected human cases. These viruses are genetically closely linked to the 2006-2007 isolates from Kenya. PMID:22608405</p> <div class="credits"> <p class="dwt_author">Cêtre-Sossah, Catherine; Zeller, Hervé; Grandadam, Marc; Caro, Valérie; Pettinelli, François; Bouloy, Michèle; Cardinale, Eric; Albina, Emmanuel</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-06-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">352</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/5632323"> <span id="translatedtitle">Experiments on <span class="hlt">rift</span> zone evolution in unstable volcanic edifices</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Large ocean island volcanoes frequently develop productive <span class="hlt">rift</span> zones located close to unstable flanks and sites of older major sector collapses. Flank deformation is often caused by slip along a décollement within or underneath the volcanic edifice. We studied how such a stressed volcanic flank may bias the <span class="hlt">rift</span> zone development. The influence of basal lubrication and lateral flank creep</p> <div class="credits"> <p class="dwt_author">Thomas R. Walter; Valentin R. Troll</p> <p class="dwt_publisher"></p> <p class="publishDate">2003-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">353</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40847845"> <span id="translatedtitle">A plume head melting under a <span class="hlt">rifting</span> margin</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">A large igneous province (LIP), in the form of a long narrow band of thickened oceanic crust, runs along the Atlantic margin of North America abutting the <span class="hlt">rifted</span> continental shelf. We propose that this, like many other LIPs, has a mantle plume origin. There is evidence that when the central Atlantic Ocean opened the <span class="hlt">rift</span> was underlain by the flattened</p> <div class="credits"> <p class="dwt_author">A. M. Leitch; G. F. Davies; M. Wells</p> <p class="dwt_publisher"></p> <p class="publishDate">1998-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">354</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40447769"> <span id="translatedtitle">The Dead Sea <span class="hlt">Rift</span>: lateral displacement and downfaulting phases</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">A sinistral strike slip of 105 km along the Dead Sea <span class="hlt">Rift</span> is confirmed by the continuity in the restored trend of Eocene sedimentary belts. Yet, the similar characteristics on either side of the <span class="hlt">Rift</span> between the Upper Miocene conglomerates, mudstones and lithographic limestones (particularly the Kefar Gil'adi Fm.) and the Pliocene marls, oolitic limestones and basalts (e.g., Bira Fm.,</p> <div class="credits"> <p class="dwt_author">A. Sneh</p> <p class="dwt_publisher"></p> <p class="publishDate">1996-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">355</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2003LPI....34.1610Z"> <span id="translatedtitle">Extension Across Valles Marineris and the Thaumasia "<span class="hlt">Rift</span>", Mars</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">We calculate extension from topographic profiles. We find the extension across the "Thaumasia <span class="hlt">Rift</span>" (0.5-4.5 km), a large and complex graben sytem in the Claritas Fossae region, comparable to that across the Tempe Fossae <span class="hlt">Rift</span> (2.5-3.1 km), but much lower than across Valles Marineris (9-20 km).</p> <div class="credits"> <p class="dwt_author">Zuschneid, W.; Hauber, E.; Kronberg, P.; Jaumann, R.</p> <p class="dwt_publisher"></p> <p class="publishDate">2003-03-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">356</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/49828488"> <span id="translatedtitle">High-Technology Investigations Of <span class="hlt">Rift</span> Propogation And Plate Tectonics</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Plate tectonics as originally formulated was so successful in revolutionizing geology that only very few modifications have been necessary. One of these modifications is the suggestion that spreading centers sometimes increase their length by propagation, progressively <span class="hlt">rifting</span> apart preexisting lithospheric plates and reorganizing the Earth's plate boundary geometry. This small change to plate tectonic theory, known as the propagating <span class="hlt">rift</span></p> <div class="credits"> <p class="dwt_author">R. Hey</p> <p class="dwt_publisher"></p> <p class="publishDate">1983-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">357</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.agu.org/journals/jb/v087/iB13/JB087iB13p10677/JB087iB13p10677.pdf"> <span id="translatedtitle">Continental <span class="hlt">Rifting</span> and the Implications For Plate Tectonic Reconstructions</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Previous plate tectonic reconstructions have tried to recreate the pre-rifiing (Pangea) configuration of the continents by matching contours or lineaments that are thought to represent the continental boundaries. Such reconstructions have the inherent assumptions that no extension occurs within the continent during <span class="hlt">rifting</span>, that the continental boundaries are isochrons, and that the continents <span class="hlt">rift</span> without distortion. This paper proposes a</p> <div class="credits"> <p class="dwt_author">Gregory E. Vink</p> <p class="dwt_publisher"></p> <p class="publishDate">1982-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">358</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/5278708"> <span id="translatedtitle">Urban Integrated Industrial Cogeneration <span class="hlt">Systems</span> Analysis. Phase II <span class="hlt">final</span> report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">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> <div class="credits"> <p class="dwt_author">Not Available</p> <p class="dwt_publisher"></p> <p class="publishDate">1984-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">359</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009EGUGA..11.7560M"> <span id="translatedtitle">Understanding the tectono-sedimentary record of crustal thinning and mantle exhumation at deep-<span class="hlt">rifted</span> margins</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Classical <span class="hlt">rift</span> models are unable to predict the tectono-sedimentary evolution observed at deep water, magma-poor <span class="hlt">rifted</span> margins. At present the processes controlling crustal thinning and mantle exhumation are not yet understood and little is known about the associated syn-tectonic sedimentary <span class="hlt">system</span>. This is mainly due to the lack of examples and data from present-day active <span class="hlt">systems</span>. One of the best natural laboratories to explore the evolution of crustal thinning and mantle exhumation and its related syn-tectonic sedimentary record are the remnants of the ancient Tethys margins exposed in the Lower Austroalpine and South Penninic units in the Alps in SE Switzerland. The reconstructed architecture of the Jurassic <span class="hlt">rifted</span> margin enables to demonstrate a very contrasting evolution of the proximal and distal margins, the former showing classical fault-bounded <span class="hlt">rift</span> basins whereas the latter preserving a spectacular <span class="hlt">rift</span>-related detachment <span class="hlt">system</span>. The goal of this presentation is to discuss the relation between crustal thinning and mantle exhumation accommodated by detachment <span class="hlt">systems</span> and the related stratigraphic and sedimentary evolution. The <span class="hlt">rift</span>-related detachment <span class="hlt">system</span> is exposed within two nappes, the Bernina and Err nappes. While in the Bernina nappe syn- and post-<span class="hlt">rift</span> sediments are only locally preserved onlapping onto a top-basement detachment fault, in the Err nappe a complete syn-<span class="hlt">rift</span> sedimentary record is preserved and can be mapped over an area of about 50 km2 within the Samedan zone. The syn-<span class="hlt">rift</span> sedimentary sequence can be subdivided into 4 units, which are in a stratigraphic order from bottom to top the Bardella, the Saluver A, Saluver B, and Saluver C units. The Bardella unit consists of sedimentary breccias that result from the reworking of the Triassic to Lower Jurassic carbonate platform. This unit is dominated by debris-flow dominated processes which become less mature up-section, interpreted to be related to the onset of the Err detachment leading to the break-up of the Triassic to Early Jurassic pre-<span class="hlt">rift</span> carbonate platform. The Saluver A unit, consisting of reworked basement rocks, is interpreted to represent the first depositional unit documenting the exhumation at the seafloor and reworking of basement rocks along a top-basement detachment fault, resulting in a new source and the establishment of a siliciclastic sedimentary <span class="hlt">system</span>. The Saluver B and C units represent the onset and evolution of a more mature siliciclastic turbidite <span class="hlt">system</span>. The turbidite currents are funneled along complex tectonic inherited structures that connect the source (Bernina) with the basin (most distal Err domain). The interfingering of Saluver A and B units suggests a progressive change from a local tectono-sedimentary <span class="hlt">system</span> developing into a large-scale axial turbiditic <span class="hlt">system</span>. The transition between Saluver B to C seems to characterize the progressive migration of tectonic activity into the zone of exhumed continental mantle further outboard and the general decreasing of the sedimentation rate as documented in the upper Saluver C low-energy deposits. Each of the 4 syn-tectonic sedimentary units document a change in the style of deformation from high-angle normal faulting resulting in the break-up of the pre-<span class="hlt">rift</span> carbonate platform (e.g Bardella unit), to crustal thinning and exhumation of basement rocks along detachment faults (Saluver A and B units) and the migration of deformation further outboard resulting in a sag type basin (Saluver C unit). Assessing the syn-tectonic sedimentary record of crustal thinning and mantle exhumation is a key to elaborate new predictive genetic models for the evolution of deep, magma-poor <span class="hlt">rifted</span> margins.</p> <div class="credits"> <p class="dwt_author">Masini, E.; Mohn, G.; Manatschal, G.; Ghienne, J. F.; Lafont, F.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-04-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">360</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011AGUFM.T43G2473F"> <span id="translatedtitle">Mountain Building in interior East Antarctica caused by Continental <span class="hlt">Rifting</span> around a Stalled Precambrian Orogen</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Gamburtsev Subglacial Mountains are the least understood tectonic feature on Earth, as they are completely hidden beneath the East Antarctic Ice Sheet. The paradox of their high elevation and youthful Alpine topography, but location on the East Antarctic craton, has puzzled researchers since their first discovery in 1958. Recent studies suggest that the preservation of Alpine topography in the Gamburtevs reflects extremely low long-term erosion rates beneath the East Antarctic Ice Sheet. However, the origin of the Gamburtsevs remains problematic within the plate tectonic paradigm. Here we present the first comprehensive view of the crustal architecture and uplift mechanisms for the Gamburtsevs derived from new radar, gravity and magnetic data collected as part of AGAP, a flagship project of the International Polar Year. The geophysical data define a 2500 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 Meso or Paleoproterozoic assembly of East Antarctica, was preserved as in some other Paleozoic and Proterozoic orogens and rejunvenated during much later Permian (ca 280 Ma) and Cretaceous (ca 100 Ma) <span class="hlt">rifting</span>. Much like East Africa, the interior of East Antarctica appears to be a mosaic of Precambrian provinces affected by continental <span class="hlt">rifting</span> processes. Our flexural 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 both the high-elevation and relief of the Gamburtsevs. The evolution of the Gamburtsevs demonstrates that continental <span class="hlt">rifting</span> and preserved orogenic roots can produce broad regions of high topography within continental interiors without significantly modifying the underlying Precambrian lithosphere.</p> <div class="credits"> <p class="dwt_author">Ferraccioli, F.; Finn, C.; Jordan, T. A.; Bell, R. E.; Anderson, L.; Damaske, D.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-12-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_17");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a onClick='return showDiv("page_3");' href="#">3</a> <a onClick='return 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href="#">11</a> <a onClick='return showDiv("page_12");' href="#">12</a> <a onClick='return showDiv("page_13");' href="#">13</a> <a onClick='return showDiv("page_14");' href="#">14</a> <a onClick='return showDiv("page_15");' href="#">15</a> <a onClick='return showDiv("page_16");' href="#">16</a> <a onClick='return showDiv("page_17");' href="#">17</a> <a onClick='return showDiv("page_18");' href="#">18</a> <a style="font-weight: bold;">19</a> <a onClick='return showDiv("page_20");' href="#">20</a> <a onClick='return showDiv("page_21");' href="#">21</a> <a onClick='return showDiv("page_22");' href="#">22</a> <a onClick='return showDiv("page_23");' href="#">23</a> <a onClick='return showDiv("page_24");' href="#">24</a> <a onClick='return showDiv("page_25");' href="#">25</a> </span> </span> <a id="NextPageLink" onclick='return showDiv("page_20");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">361</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013JGRB..118.1109M"> <span id="translatedtitle">The stress shadow induced by the 1975-1984 Krafla <span class="hlt">rifting</span> episode</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">It has been posited that the 1975-1984 Krafla <span class="hlt">rifting</span> episode in northern Iceland was responsible for a significant drop in the rate of earthquakes along the Húsavík-Flatey Fault (HFF), a transform fault that had previously been the source of several magnitude 6-7 earthquakes. This compelling case of the existence of a stress shadow has never been studied in detail, and the implications of such a stress shadow remain an open question. According to rate-state models, intense stress shadows cause tens of years of low seismicity rate followed by a faster recovery phase of rate increase. Here, we compare the long-term predictions from a Coulomb stress model of the <span class="hlt">rifting</span> episode with seismological observations from the SIL catalog (1995-2011) in northern Iceland. In the analyzed time frame, we find that the <span class="hlt">rift</span>-induced stress shadow coincides with the eastern half of the fault where the observed seismicity rates are found to be significantly lower than expected, given the historical earthquake activity there. We also find that the seismicity rates on the central part of the HFF increased significantly in the last 17 years, with the seismicity progressively recovering from west to east. Our observations confirm that rate-state theory successfully describes the long-term seismic rate variation during the reloading phase of a fault invested by a negative Coulomb stress. Coincident with this recovery, we find that the b-value of the frequency-magnitude distribution changed significantly over time. We conclude that the <span class="hlt">rift</span>-induced stress shadow not only decreased the seismic rate on the eastern part of the HFF but also temporarily modified how the <span class="hlt">system</span> releases seismic energy, with more large magnitude events in proportion to small ones. This behavior is currently being overturned, as <span class="hlt">rift</span>-induced locking is now being compensated by tectonic forcing.</p> <div class="credits"> <p class="dwt_author">Maccaferri, F.; Rivalta, E.; Passarelli, L.; Jónsson, S.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-03-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">362</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2007JGRB..112.3103G"> <span id="translatedtitle">Is the Bounty Trough off eastern New Zealand an aborted <span class="hlt">rift</span>?</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Remarkably little is known about the Cretaceous <span class="hlt">rifting</span> process between New Zealand and Antarctica that affected the submarine regions within the New Zealand microcontinent. Bounty Trough provides insights into these breakup processes. Here we present results from a combined gravity, multichannel seismic, and wide-angle reflection/refraction seismic transect across the Middle Bounty Trough and interpret these results on the basis of velocity distribution and crustal composition derived from Poisson's ratio and P-wave velocity. The lower crust exhibits a high-velocity (vp ? 7 - 7.7 km/s, vs ? 3.9 - 4.5 km/s), high-density (? = 3.02 kg/cm3) body at the location of the thinnest crust on the profile. Here the crustal thickness is reduced to about 9 km from 22-24 km beneath Chatham Rise and Campbell Plateau. We interpret the high-velocity/density body as a magmatic intrusion into thinned continental crust. Our results show that the Cretaceous opening of Bounty Trough was very likely not the result of back-arc extension caused by collision of the Hikurangi Plateau with the Gondwana margin, but of continental breakup processes related to the separation of New Zealand from Antarctica. <span class="hlt">Rifting</span> ceased in the Middle Bounty Trough at the onset of seafloor spreading. Comparisons with the Oslo <span class="hlt">Rift</span> and the Ethiopian/Kenya <span class="hlt">Rift</span> indicate that all three <span class="hlt">rift</span> <span class="hlt">systems</span> show analogous extensional features. From this we derive a stretching model for the Bounty Trough that combines elements of pure shear and simple shear extension.</p> <div class="credits"> <p class="dwt_author">Grobys, J. W. G.; Gohl, K.; Davy, B.; Uenzelmann-Neben, G.; Deen, T.; Barker, D.</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-03-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">363</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.cotf.edu/ete/modules/rift/rift.html"> <span id="translatedtitle">Exploring the Environment: <span class="hlt">Rift</span> Valley Fever</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://nsdl.org/nsdl_dds/services/ddsws1-1/service_explorer.jsp">NSDL National Science Digital Library</a></p> <p class="result-summary">Students will study the nature and transmission of the <span class="hlt">Rift</span> Valley fever virus to determine ways to prevent an outbreak. This is one of several interdisciplinary problem-based learning modules for high school and middle school students addressing real-world problems in environmental earth science. Teacher pages include module notes, software information, and a teacher-to-teacher message board to share/borrow ideas for planning, facilitating, and assessing information. Situations and very clear instructions are given on how to implement problem-based learning in the classroom.</p> <div class="credits"> <p class="dwt_author">University, Classrooms O.; Program, Nasa L.; University, Wheeling J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">364</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012EGUGA..14.6354B"> <span id="translatedtitle">Evolution of post-<span class="hlt">rift</span> sediment transport on a young <span class="hlt">rifted</span> margin : Insights from the eastern part of the Gulf of Aden</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The formation of gravity-driven sedimentary <span class="hlt">systems</span> on continental <span class="hlt">rifted</span> margins results from the interaction between climate, ocean currents and tectonic activity. During the early stages of margin evolution, the tectonic processes are probably as important as climate for the sedimentary architecture. Therefore, the young margins (ca. 35 Ma) of the Gulf of Aden provide the opportunity to evaluate the respective roles of monsoon and tectonic uplift in the formation and evolution through the post-<span class="hlt">rift</span> period of gravity-driven deposits (Mass Transport Complexes (MTCs) and deep-sea <span class="hlt">systems</span>) on the continental slopes and in the oceanic basin respectively. Here we present a combined geomorphologic and stratigraphic study of the northern margin (Oman and Yemen) and the southern margin (Socotra island), in which we classified and interpreted the gravity-driven processes, their formation and their evolution during the post-<span class="hlt">rift</span> period. The interpretation of seismic lines reveals the presence of bottom currents since the drift phase, suggesting that the Gulf of Aden was connected to the world oceans at that time. An abrupt depositional change affected the eastern basin of the Gulf of Aden around 10 Ma or thereafter (Chron 5), characterised by the first occurrence of deep sea fans and an increase in the number of MTCs. The first occurrence of MTCs may be explained by the combined 2nd-3rd order fall of the relative sea-level (Serravalian/Tortonian transition). This variation of relative sea level combined with a climatic switch (Asian monsoon onset around 15 Ma and its intensification around 7-8 Ma) control the sediment flux. The youngest unit of the post-<span class="hlt">rift</span> supersequence is characterised by a second important MTC occurrence that is restricted to the eastern part of the deep basin. This is caused by a late uplift of the northern and southern margins witnessed onshore by the presence of young stepped marine terraces.</p> <div class="credits"> <p class="dwt_author">Baurion, C.; Gorini, C.; Leroy, S.; Lucazeau, F.; Migeon, S.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-04-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">365</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/17627440"> <span id="translatedtitle">Spatial risk assessment of <span class="hlt">Rift</span> Valley fever in Senegal.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary"><span class="hlt">Rift</span> Valley fever (RVF) is broadening its geographic range and is increasingly becoming a disease of global importance with potentially severe consequences for human and animal health. We conducted a spatial risk assessment of RVF in Senegal using serologic data from 16,738 animals in 211 locations. Bayesian spatial regression models were developed with interpolated seasonal rainfall, land surface temperature, distance to perennial water bodies, and time of year entered as fixed-effect variables. Average total monthly rainfall during December-February was the most important spatial predictor of risk of positive RVF serologic status. Maps derived from the models highlighted the lower Senegal River basin and the southern border regions of Senegal as high-risk areas. These risk maps are suitable for use in planning improved sentinel surveillance <span class="hlt">systems</span> in Senegal, although further data collection is required in large areas of Senegal to better define the spatial distribution of RVF. PMID:17627440</p> <div class="credits"> <p class="dwt_author">Clements, Archie C A; Pfeiffer, Dirk U; Martin, Vincent; Pittliglio, Claudia; Best, Nicky; Thiongane, Yaya</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">366</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2002AGUFM.T72A1238B"> <span id="translatedtitle">The Initiation of Arc <span class="hlt">Rifting</span> in the Formation of Back-Arc Basins: An Example from the Southern Mariana Arc</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">A MR-1 bathymetry and sidescan sonar survey in 2001 identified a previously unknown <span class="hlt">rift</span> valley in the southern Mariana Arc region, which represents the extreme southwestern end of backarc extension in this <span class="hlt">system</span>. This valley is ~100 km long and has 2 km of relief, and in profile has the morphology of a half-graben with a 45° dipping fault scarp forming the north-western wall in the West Mariana Ridge. A dredge haul from this scarp recovered a wide range of arc lithologies, from altered ankaramite to beach rock. The graben floor gently slopes upward and southeastward and terminates in a forearc horst block which appears to have once been almost subaerial, as dredged samples from it consisted largely of shallow-water corals. This block now lies between 1500 to 2500 m below sea level. Unlike the rest of the Mariana Backarc, the <span class="hlt">rifting</span> does not appear to be accompanied by magmatism and therefore seafloor spreading is not taking place. Small volcanoes are present, though axial floor-covering lava flows common in spreading centers are not seen. The morphology and distribution of volcanism is similar here to the incipient backarc <span class="hlt">rifts</span> of the Izu arc at the Sumisu <span class="hlt">Rift</span>. The area is seismically active and earthquakes occurring beneath the <span class="hlt">rift</span> graben have normal centroid moment tensor solutions and shallow(<50km) depths, consistent with still-active <span class="hlt">rifting</span>. This graben appears to be the result of the <span class="hlt">rifting</span> of arc lithosphere, but it has not yet reached the stage where volcanism forms new crust. At the center of extension ~50 km to the east of this <span class="hlt">rift</span> graben, small arc volcanoes sit in heavily fractured terrain, and another ~100 km further eastward is a robust spreading segment. This small geographic area is an ideal setting for the study of linkages between deformation of arc lithosphere and production of arc magmas in the early phases of the subduction factory. What is unique about this part of the Southern Mariana subduction factory is that the trend of the slab and associated magmatism extends unbroken along the entire southern margin of the <span class="hlt">system</span>, yet the lithospheric deformation cross-cuts the volcanic arc trend obliquely. This causes amagmatic <span class="hlt">rifting</span> to cut through the inner forearc, arc volcanism to be interrupted by magmatic <span class="hlt">rift</span> genesis, and larger discrete arc volcanoes to merge with a robust <span class="hlt">rift</span> segment. Therefore, changes seen while moving along the center of backarc extension in space may correspond to changes of the center of extension with time. If true, then this <span class="hlt">rift</span> graben would represent the earliest stage of extension in this backarc basin. Furthermore, since these changes take place over such a short distance in this <span class="hlt">system</span>, it suggests that the transition from early <span class="hlt">rifting</span> to robust spreading in backarcs could occur rapidly.</p> <div class="credits"> <p class="dwt_author">Becker, N. C.; Fryer, P.; Martinez, F.</p> <p class="dwt_publisher"></p> <p class="publishDate">2002-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">367</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/36438772"> <span id="translatedtitle">The NSm proteins of <span class="hlt">Rift</span> Valley fever virus are dispensable for maturation, replication and infection</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary"><span class="hlt">Rift</span> Valley fever (RVF) virus belongs to the Bunyaviridae family of segmented negative-strand RNA viruses and causes mosquito-borne disease in sub-Saharan Africa. We report the development of a T7 RNA polymerase-driven plasmid-based genetic <span class="hlt">system</span> for the virulent Egyptian isolate, ZH501. We have used this <span class="hlt">system</span> to rescue a virus that has a 387 nucleotide deletion on the genomic M segment</p> <div class="credits"> <p class="dwt_author">Sonja R. Gerrard; Brian H. Bird; Cesar G. Albariño; Stuart T. Nichol</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">368</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010AGUFM.T24C..07T"> <span id="translatedtitle">Two-dimensional surface velocity field across the Asal <span class="hlt">Rift</span> (Afar Depression) from 11 years of InSAR data</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">We analyze two-dimensional surface velocity maps of the 200x400 km2 region covering the Asal <span class="hlt">Rift</span> located at the western tip of the Aden Ridge, using the 1997-2008 archive of InSAR data from the RADARSAT satellite. The large phase signal due to turbulent tropospheric conditions over the Afar region is mostly removed from the 11-year average line of sight (LOS) velocity maps, revealing a clear deformation signal across the <span class="hlt">rift</span>. Assuming the horizontal velocity to be parallel to the direction predicted by the Arabia/Somalia rotation pole (Vigny et al., 2007), we compute the fields of the vertical and horizontal components of the velocity from the ascending and descending line of sight (LOS) velocity maps. The horizontal velocity field shows the divergence between the Arabia and Somalia plates concentrated along the Asal <span class="hlt">rift</span>, and veering toward the south-west, into the Derella-Gaggade basin <span class="hlt">system</span>. The Asal <span class="hlt">rift</span> shoulders open at a rate of ~15 mm/yr, while the horizontal velocity decreases away from the <span class="hlt">rift</span> down to the plate motion rate of ~11-12 mm/yr. The vertical velocity field shows a ~60 km wide zone of doming centered over the <span class="hlt">rift</span> associated with shoulder uplift and subsidence of the <span class="hlt">rift</span> inner floor. The differential movement between the shoulders and the <span class="hlt">rift</span> floor is accommodated by two main antithetic faults: the south-dipping Fault ? well developed in the topography and the recent north-dipping Fault E with a small topographic scarp. We explain the observed velocity field with 2D-forward and 3D-inverse models combining dislocations of rectangular elements in an elastic half-space. The forward model allows us to estimate the overall geometry and rates of an inflating body at 5 km depth (represented by a combination of a dike and a horizontal sill) and creep on two faults. The least-squares inverse model shows an inflating body located under the Fieale volcano expanding at 2 106 m3/yr. Faults bordering the <span class="hlt">rift</span> show down-dip and opening motion especially at their base where they are connected to the inflating body. Comparison of the total geometric moment rate due to the opening of all modelled structures and the total volume of magma estimated to have been mobilized during the 1978 seismo-magmatic event suggests that the <span class="hlt">system</span> may still be in a transient mode, as the current inflation rate would accumulate the same volume in 40-50 years.</p> <div class="credits"> <p class="dwt_author">Tomic, J.; Peltzer, G.; Doubre, C.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">369</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010EGUGA..1212527T"> <span id="translatedtitle">Integration of geophysical and geochemical data for the study of the North-Est <span class="hlt">Rift</span> dynamics on Mount Etna volcano</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Mount Etna volcano is located at the front of the Apennine-Maghrebian Chain, along the Malta Escarpment, and lies on the Pliocene-Pleistocene foredeep deposits. The apparatus is characterized by a central conduit divided, at surface, into four summit craters, with a maximum elevation of 3329 m above sea level. In the upper part (>1500 m), three main "<span class="hlt">rift</span> zones" can be identified: the NE <span class="hlt">Rift</span>, the S <span class="hlt">Rift</span> and the W <span class="hlt">Rift</span>. These structures are probably shallow, do not tap deep magma and are usually directly fed by the central conduit, rather than from an underlying shallow magma chamber. The volcano is characterized by the displacement of its eastern to southern flanks, involving an on-shore area of >700 km2. This is confined to the north by the Pernicana fault <span class="hlt">system</span> (PFS). The PFS, located on the NE sector of Mt. Etna, is >18 km long, from the NE <span class="hlt">Rift</span> to the coastline. The western PFS is seismogenetic, while the eastern PFS undergoes creep movements. In its westernmost section, the PFS is divided into two main segments, the more northerly of these starting from the Monte Nero area of the NE <span class="hlt">Rift</span> and the more southerly from Piano Provenzana. The PFS is kinematically connected, with a feedback mechanism, to eruptions occurring on the NE <span class="hlt">Rift</span>. In spite of this relationship, the PFS has shown continuous activity between 1947 and 2002, a period when no eruptions occurred on the NE <span class="hlt">Rift</span>, with major surface fracturing and seismic activity in 1984-1988. Geophysical-geochemical investigation were conducted in the area where PFS is connected with the NE <span class="hlt">Rift</span>, including the areas characterized by a consistent slip, as well as those structures through which the motion occurs. The aim of this work is to provide a multidisciplinary frame to characterize this dynamic and structural natural <span class="hlt">system</span>. Magnetotelluric, geoelectric, self-potential and and soil gas emissions measurements give a comprehensive view on the geometry and depth of the lithological units together with fluid circulation insights. Here, the sedimentary basement, detected by the resistivity models, interfaces media with different physical characteristics where fluids flow play a crucial role interacting onto the Pernicana fault activity.</p> <div class="credits"> <p class="dwt_author">Tripaldi, Simona; Balasco, Marianna; Lapenna, Vincenzo; Loddo, Mariano; Moretti, Pierpaolo; Neri, Marco; Piscitelli, Sabatino; Romano, Gerardo; Schiavone, Domenico; Siniscalchi, Agata</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-05-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">370</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/658132"> <span id="translatedtitle">Acoustic Resonance Spectroscopy (ARS) Munition Classification <span class="hlt">System</span> enhancements. <span class="hlt">Final</span> report</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">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> <div class="credits"> <p class="dwt_author">Vela, O.A.; Huggard, J.C.</p> <p class="dwt_publisher"></p> <p class="publishDate">1997-09-18</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">371</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011AGUFM.T33D2455B"> <span id="translatedtitle">Geodetic determination of plate velocity vector in the Ethiopia <span class="hlt">Rift</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Red sea, Gulf of Aden and the Main Ethiopian <span class="hlt">rift</span> form a triple junction in the Afar Region. Although the East African <span class="hlt">Rift</span>, the divergent plate boundary between Nubian and Somalia, is often cited as a modern archetype for <span class="hlt">rifting</span> and continental breakup, its current kinematics is the least known of all major plate boundaries. Moreover, geodetic datum in such tectonically active area is subject to distortion that increases with time. Therefore, a close study of the positions and velocities of reference stations in such tectonic active areas is necessary, if one wants to have high precise geodetic measurement for any developmental activity. In this study phase and pseudo-range GPS measurements were processed to derive the daily solutions of positions in reference to the ITRF05. This solution from 8 continuous stations in Ethiopia, with a length of 0.75 to 2.67 years, is then combined into a cumulative solution with position and velocity estimates. Here a method that combines GPS observation data from 2007 to 2009 to estimate time-dependent motion of stations in a region of active deformation is implemented. First, observations were analysed separately to produce loosely constrained estimates of station positions and coordinate <span class="hlt">system</span> parameters which are then combined with appropriate constraints to estimate velocities and co-seismic displacements. The result archived gives a good insight about the velocity at which the three major plates, namely the Nubian, Arabian and Somalia plates are moving with respect to each other. The study shows the relative velocity between Nubia and Somalia plates with 4.6±0.3 mm/yr. While, the Nubia and Arabia plates are moving with 33±0.15mm/yr.Moreover; positions of stations are computed with high precession for any future reference purpose. Due to short duration of measurements at some stations further observation are recommended to compute positions and velocity fields after all stations have data at least for two years time. Key words: GPS, Space geodesy, ITRF05, Deformation</p> <div class="credits"> <p class="dwt_author">Boku, E.; Teklemariam, E.; Rivalta, E.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">372</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2007AGUFM.T34A..02M"> <span id="translatedtitle">From Crustal Thinning to Continental Break-up in Magma-Poor <span class="hlt">Rifted</span> Margins: How Important are Detachment Faults?</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Detachment faults are widely regarded as playing an important role in crustal thinning and mantle exhumation at magma-poor <span class="hlt">rifted</span> margins. However, how important are these structures and what is their role in crustal thinning and mantle exhumation? In our presentation, we review the pertinent observations made along the Iberia-Newfoundland, Western Pyrenees-Bay of Biscay and the Alpine margins. A reconstruction of the future distal margins 10 to 20 myr before continental break-up shows that: (1) extension was localized and the crust was thinned to less than 10 km despite subdued high-angle normal faulting, (2) detachment faults responsible for mantle unroofing are late and shallow crustal structures, (3) the mantle lithosphere was locally omitted and replaced by infiltrated asthenospheric mantle, and (4) shallow marine sediments were deposited over thinned crust suggesting a retardation of tectonic subsidence. These observations scrutinize our present knowledge of <span class="hlt">rift</span> processes and ask for a paradigm shift in the way to interpret <span class="hlt">rifted</span> margins. To further investigate the role of detachment faulting during crustal thinning and mantle exhumation, we developed a numerical model that: (1) uses initial conditions, strain distribution, rheology and deformation modes constrained from the study of Alpine margins, and (2) is able to replicate the well-documented tectonic evolution of the Iberia and Alpine margins, starting with pure-shear dominated crustal stretching and ending with mantle exhumation along detachment faults. The most interesting result of the experiment is the way the model evolves from the prescribed initial distributed stretching (e.g. pure-shear) to <span class="hlt">final</span> localized exhumation (e.g. simple shear). During this transitional phase, referred to as thinning phase, extension is accommodated by a <span class="hlt">system</span> of superimposed but decoupled concave-downward faults that simultaneously exhume middle crust to the seafloor and deeper mantle at the base of the crust. The two rolling hinges eventually merge to form one concave downward fault that unroofs the mantle to the seafloor. These results suggest that exhumation associated with detachment faulting is an important process. It can explain crustal thinning to less than 10 km; the lack of major fault bounded topography; and the emplacement of deep and infiltrated mantle rocks beneath thinned crust 10 to 20 myr before continental break-up. This has important consequences for the isostatic, thermal and rheological evolution of deep magma-poor margins that need to be constrained by data. At present, the thinning mode is neither understood nor constrained by geological or geophysical data. Because the proximal and distal margins are mainly preserving structures of the initial stretching and the <span class="hlt">final</span> exhumation modes, we started to investigate the transition zone between the proximal and distal margins in the Alps and the zone ahead of a propagating ocean in the Western Pyrenees - Bay of Biscay. In our presentation, we present evidence for the existence of the thinning mode within these two domains and show how these results help to develop new conceptual ideas to re-interpret seismic data from present-day magma-poor <span class="hlt">rifted</span> margins.</p> <div class="credits"> <p class="dwt_author">Manatschal, G.; Lavier, L. L.; Péron-Pinvidic, G.; Jammes, S.; Mohn, G.; Muntener, O.</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">373</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40447873"> <span id="translatedtitle">A fully dynamic model of continental <span class="hlt">rifting</span> applied to the syn-<span class="hlt">rift</span> evolution of sedimentary basins</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">A numerical technique has been developed to model dynamically lithosphere deformation and faulting. The method is based on the theory of generalised functions and has been used to investigate <span class="hlt">rifting</span> processes in a two-layered lithosphere with up to four faults. Among other things, the method allows: (1) incorporation of the influence of syn-<span class="hlt">rift</span> erosion and sedimentary loading on fault growth;</p> <div class="credits"> <p class="dwt_author">V. I. Starostenko; V. A. Danilenko; D. B. Vengrovitch; K. N. Poplavskii</p> <p class="dwt_publisher"></p> <p class="publishDate">1996-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">374</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010AGUFM.T24C..06D"> <span id="translatedtitle">GPS Velocity Field at the Western Tip of the Aden Ridge ; Implications for <span class="hlt">Rifting</span> and the Arabia-Somalia-Nubia Triple Junction Dynamics</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Due to the presence of magma and a complex thermal structure, the dynamics of divergent plate boundaries are complicated, with microseismicity (ML<4) contributing very little to the total moment release. For the last 35 years several geodetic campaigns have been conducted at the western tip of the Aden Ridge propagating on land into Afar (Republic of Djibouti). The first segment above water, the Asal <span class="hlt">Rift</span>, experienced a seismo-volcanic event in 1978, which was the first <span class="hlt">rifting</span> episode, along with the 1978-1985 Icelandic Krafla event, to be monitored by terrestrial geodetic measurements. These measurements revealed the opening of two 1-2 m-wide dykes in the <span class="hlt">rift</span> inner floor. Since then, terrestrial and spatial geodetic monitoring shows that the <span class="hlt">rift</span> kept opening, during the post-<span class="hlt">rifting</span> period, at a rate largely exceeding the plates’ motions. This significant opening rate is decreasing with time to tend, three decades after the <span class="hlt">rifting</span> event, to the far-field opening rate. We present here the results of the GPS measurements of a 45 site network covering the Tadjoura-Asal <span class="hlt">Rift</span> <span class="hlt">System</span>, previously made every two years from 1995 to 2003, and repeated in 2010. The calculated 1999-2010 horizontal velocity field is very homogeneous with a quasi-constant N045° direction with respect to Somalia and a regular increase from the southern to the northern margin of the Asal <span class="hlt">Rift</span> clearly controlled by a few normal faults, and reaching a maximum of 12.5 mm/yr. A non-negligible part of the Arabia-Somalia divergent movement (1 to 2 mm/yr) is observed south of this <span class="hlt">rift</span>, which sheds light on the role of the active normal faults bounding the asymmetrical Gaggadé Basin and therefore brings important constraints on the location of the Red Sea Ridge-Aden Ridge-East African <span class="hlt">Rift</span> triple junction. Since the last 2003 campaign, the lack of micro-seismicity within the Asal <span class="hlt">Rift</span> seems to be associated with a ˜2 mm/yr decrease of the opening rate deduced from the GPS time series analysis. These results confirm the importance of non-steady state behavior of the Asal volcano-tectonic <span class="hlt">rift</span> segment, and the role of geothermal/volcanic activity on the occurrence of transients, as suggested by InSAR results.</p> <div class="credits"> <p class="dwt_author">Doubre, C.; Socquet, A.; Masson, F.; Cressot, C.; Mohamed, K.; Vigny, C.; Ruegg, J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">375</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2005AGUFM.T43B1408H"> <span id="translatedtitle">Fault Architecture Within the Eastern Terror <span class="hlt">Rift</span>, Western Ross Sea, Antarctica</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Terror <span class="hlt">Rift</span> is a zone of intraplate deformation within the Antarctica plate. Association with Late Cenozoic volcanic rocks and fault scarps on the seafloor indicates neotectonic to recent activity. Intraplate extension and transtension associated with regional strike-slip deformation have both been proposed for the Terror <span class="hlt">Rift</span> by previous workers. Marine seismic data across the Terror <span class="hlt">Rift</span>, western Ross Sea, Antarctica, is revealing new details of neotectonic <span class="hlt">rift</span> geometry. An area of 30km by 90km near the Drygalski Ice Tongue where the spacing of E-W lines is at a minimum was selected for detailed study. There are three structural components in the study area: a central arch structure flanked by two opposing dip domains bounded by border fault <span class="hlt">systems</span>. The central arch shows two phases of fault activity. An early localized faulting episode produced a symmetric graben truncated by an erosional unconformity. Later, some preexisting faults were reactivated, cutting through the angular unconformity and reaching up to, and in places displacing, the seafloor. The second faulting phase formed a larger symmetric graben, c. 14 km across. Maximum stratal displacement across the graben boundary faults are 0.30ms on the east, and 0.45ms on the west. The two bounding border fault regions, one 15km to the west and the other 10km to the east of the main arch, define a composite graben feature surrounding the main arch. The border fault <span class="hlt">systems</span> are symmetric in the north, with equal fault dips and offset magnitude. Moving southward, the western border fault <span class="hlt">system</span> has increasing offset magnitude producing a west-tilted half-graben. Minimum fault displacement across the two border fault <span class="hlt">systems</span> is an average of .10ms in the east and .40ms in the west. These structures will be traced along strike to map the 3D fault architecture of the Terror <span class="hlt">Rift</span> on a regional scale. Results to date, however, document only normal faulting in this sector of the Terror <span class="hlt">Rift</span>, suggesting extension dominates the intraplate deformation field.</p> <div class="credits"> <p class="dwt_author">Hall, J. M.; Wilson, T. J.; Henrys, S.</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">376</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/3433336"> <span id="translatedtitle">Endemic fluorosis in the Ethiopian <span class="hlt">Rift</span> Valley.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Between 1977 and 1985, the fluoride content of drinking water and the incidence of endemic fluorosis were assessed and correlated in 16 large farms, villages and towns in the Ethiopian <span class="hlt">Rift</span> Valley. The fluoride level of drinking-water collected from wells there ranged from 1.2 mg/litre to 36.0 mg/l (mean 10.0 mg/l). Dental fluorosis was observed in more than 80% of sampled children resident in the <span class="hlt">Rift</span> Valley since birth, with maximum prevalence in the age-group 10-14 years; 32% of the children showed severe dental mottling. Males were affected more than females. Three areas, Wonji-Shoa, Alemtena and Samiberta, were identified as having cases of skeletal fluorosis. The highest incidence was at Wonji-Shoa sugar estates, where a linear relationship was observed between the development of crippling fluorosis, fluoride concentration of drinking-water, and period of exposure to it. The first cases of skeletal fluorosis there appeared among workers (98% males) who had been consuming water with fluoride content of more than 8ppm for over 10 years. Among 30 workers with crippling skeletal fluorosis, cervical radiculo-myelopathy was found to be the commonest incapacitating neurologic complication. As a preventive measure, low-fluoride surface water should be supplied for drinking wherever feasible; if this is not possible, the development of partial defluoridation should be considered. PMID:3433336</p> <div class="credits"> <p class="dwt_author">Haimanot, R T; Fekadu, A; Bushra, B</p> <p class="dwt_publisher"></p> <p class="publishDate">1987-07-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">377</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/5545756"> <span id="translatedtitle">Galapagos <span class="hlt">rift</span> at 86 /sup 0/W 5. Variations in volcanism, structure, and hydrothermal activity along a 30-kilometer segment of the <span class="hlt">rift</span> valley</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">A 30-km segment of the Galapagos <span class="hlt">Rift</span> near 86 /sup 0/W has been mapped in detail using the Angus towed camera <span class="hlt">system</span>, the submersible Alvin, and multi-narrowbeam sonar data. Recent volcanic activity and active hydrothermal circulation are evident along the entire length of the segment mapped. There are, however, clear along-strike variations in these processes which render previous two-dimensional models obsolete. Although alternate explanations are possible, eruptive sequences appear to begin with the outpouring of surface-fed sheet flows and end with more channelized pillow flows. In the western portion of the <span class="hlt">rift</span> studied, sheet flows dominate with the entire valley floor covered by recent flows associated with a broad shield volcano. The eastern portion, on the other hand, is narrower; consisting primarily of less voluminous pillow flows of apparently the same youthful age. Three possible models for the volcanic evolution of this <span class="hlt">rift</span> segment are presented. According to the first model, the extrusive portion of the crust is formed by a distinct volcanic episode, followed by a long period of volcanic quiescence. The volcanic phase begins with voluminous sheet flows emerging from numerous eruptive fissures, which in time evolve into a narrow pillow ridge. Farther along-strike, where the flows are smaller and the extrusive zone narrow, the marginal portions undergo continued fissuring and subsequent uplift to form marginal highs and lows. This deformational activity also affects the extrusive zone once volcanic activity ends, converting the distinctly lobate topography of the active period into highly lineated fault-controlled terrain. According to the second model, extension and volcanism can be viewed as a continuous process without major periods of volcanic quiescence. The initial lava flows of a new eruptive sequence fill low areas, frequently spilling over local sills and flooding much of the <span class="hlt">rift</span> valley.</p> <div class="credits"> <p class="dwt_author">Ballard, R.D.; van Andel, T.H.; Holcomb, R.T.</p> <p class="dwt_publisher"></p> <p class="publishDate">1982-02-10</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">378</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011AGUFM.T31F..07D"> <span id="translatedtitle">The Salton Seismic Imaging Project: Tomographic characterization of a sediment-filled <span class="hlt">rift</span> valley and adjacent ranges, southern California</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Salton Trough in Southern California represents the northernmost <span class="hlt">rift</span> of the Gulf of California extensional <span class="hlt">system</span>. Relative motion between the Pacific and North American plates is accommodated by continental <span class="hlt">rifting</span> in step-over zones between the San Andreas, Imperial, and Cerro Prieto transform faults. Rapid sedimentation from the Colorado River has isolated the trough from the southern portion of the Gulf of California, progressively filling the subsiding <span class="hlt">rift</span> basin. Based on data from previous seismic surveys, the pre-existing continent has ruptured completely, and a new ~22 km thick crust has been created entirely by sedimentation overlying <span class="hlt">rift</span>-related magmatism. The MARGINS, EarthScope, and USGS-funded Salton Seismic Imaging Project (SSIP) was designed to investigate the nature of this new crust, the ongoing process of continental <span class="hlt">rifting</span>, and associated earthquake hazards. SSIP, acquired in March 2011, comprises 7 lines of onshore seismic refraction / wide-angle reflection data, 2 lines of refraction / reflection data in the Salton Sea, and a line of broadband stations. This presentation focuses on the refraction / wide-angle reflection line across the Imperial Valley, extending ~220 km across California from Otay Mesa, near Tijuana, to the Colorado River. The data from this line includes seventeen 100-160 kg explosive shots and receivers at 100 m spacing across the Imperial Valley to constrain the structure of the Salton Trough <span class="hlt">rift</span> basin, including the Imperial Fault. Eight larger shots (600-920 kg) at 20-35 km spacing and receivers at 200-500 m spacing extend the line across the Peninsular Ranges and the Chocolate Mountains. These data will contrast the structure of the <span class="hlt">rift</span> to that of the surrounding crust and provide constraints on whole-crust and uppermost mantle structure. Preliminary work has included tomographic inversion of first-arrival travel times across the Valley, emphasizing a minimum-structure approach to create a velocity model of the upper crust. Ongoing modeling provides constraints on the basin margins, showing a steeply dipping western edge of the <span class="hlt">rift</span> valley approximately coincident to the shoreline of the ancient Lake Cahuilla. Low velocity sediments and low velocity crystalline crust within the Imperial Valley are consistent with previous studies and contrast with faster crystalline rocks near the surface outside the <span class="hlt">rift</span>. Ongoing analysis will provide a more detailed image of upper crustal structure, as well as preliminary modeling of the entire crust.</p> <div class="credits"> <p class="dwt_author">Davenport, K.; Hole, J. A.; Stock, J. M.; Fuis, G. S.; Carrick, E.; Tikoff, B.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">379</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009AGUFM.V13E2071A"> <span id="translatedtitle">Dike injection and magma mixing in Kenya <span class="hlt">rift</span> volcanoes</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">A nexus of volcanoes in the <span class="hlt">rift</span> graben at approximately the latitude of Nairobi consist of central vent trachyte, phonolite, and peralkaline rhyolite and cinder cone and fissure-fed flows of basalt to benmoreite. The volcanoes are referred to as the Central Kenya Peralkaline Province (CKPP, Macdonald and Scaillet, 2006, Lithos 91, 59-73) and formed by a combination of processes including fractional crystallization, magma mixing, and volatile transport (Ren et al., 2006, Lithos 91, 109-124; Macdonald et al., 2008, JPet 49, 1515-1547). This presentation focuses on magma mixing for trachytes and phonolites for Suswa rocks, which are the southernmost part of the CKPP. We also explore the contribution of magma process studies to the interpretation of recent geodetic data, which indicate inflation/deflation of up to 21 cm for Kenyan volcanoes from 1997 to present (Biggs et al., 2009, Geology, in press). Incontrovertible evidence for magma mixing is found in field evidence, where a basaltic trachyandesite ash horizon is found interbedded with syncaldera trachyte (Skilling, 1993, J. Geol. Society London 150, 885-896), hand-specimen and thin-section petrography, and disequilibrium mineral chemistry. Precaldera lavas contain a homogeneous group of anorthoclase crystals with An content 6% or less. Syncaldera samples contain this same group and two other populations: polysynthetic twinned labradorite and andesine and anorthoclase with An content of 17%. Textures for all three groups indicate disequilibrium. Postcaldera flows contain the high and low An anorthoclase populations but lack the polysynthetic twinned labradorite and andesine. These observations suggest a model of injection of mafic magmas via diking into shallow trachtytic magma <span class="hlt">systems</span>. Recent geodetic studies of dike injection and subsequent seismic/volcanic activity in both Ethiopia and Lengai point to the ongoing importance of these processes to <span class="hlt">rift</span> evolution in East Africa.</p> <div class="credits"> <p class="dwt_author">Anthony, E. Y.; Espejel, V.; Biggs, J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">380</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/48517160"> <span id="translatedtitle">Lithospheric thickness beneath the southern Kenya <span class="hlt">Rift</span>: implications from basalt geochemistry</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Geochemical data are reported for samples from the flanks and floor of the southern Kenya <span class="hlt">Rift</span> Valley in the Lake Magadi area, and from two central volcanoes located within the <span class="hlt">rift</span> valley. <span class="hlt">Rift</span> lavas include samples of Singaraini and Ol Tepesi basalts on the eastern flank, Kirikiti basalts from the western flank, and plateau trachytes from the <span class="hlt">rift</span> valley floor.</p> <div class="credits"> <p class="dwt_author">Anton P. Roex; Andreas Späth; Robert E. Zartman</p> <p class="dwt_publisher"></p> <p class="publishDate">2001-01-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_18");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a onClick='return showDiv("page_3");' href="#">3</a> <a onClick='return showDiv("page_4");' href="#">4</a> <a onClick='return showDiv("page_5");' href="#">5</a> <a onClick='return showDiv("page_6");' href="#">6</a> <a onClick='return showDiv("page_7");' href="#">7</a> <a onClick='return showDiv("page_8");' href="#">8</a> <a onClick='return showDiv("page_9");' href="#">9</a> <a onClick='return showDiv("page_10");' href="#">10</a> <a onClick='return showDiv("page_11");' href="#">11</a> <a onClick='return showDiv("page_12");' href="#">12</a> <a onClick='return showDiv("page_13");' href="#">13</a> <a onClick='return showDiv("page_14");' href="#">14</a> <a onClick='return showDiv("page_15");' href="#">15</a> <a onClick='return showDiv("page_16");' href="#">16</a> <a onClick='return showDiv("page_17");' href="#">17</a> <a onClick='return showDiv("page_18");' href="#">18</a> <a style="font-weight: bold;">19</a> <a onClick='return showDiv("page_20");' href="#">20</a> <a onClick='return showDiv("page_21");' href="#">21</a> <a onClick='return showDiv("page_22");' href="#">22</a> <a onClick='return showDiv("page_23");' href="#">23</a> <a onClick='return showDiv("page_24");' href="#">24</a> <a onClick='return showDiv("page_25");' href="#">25</a> </span> </span> <a id="NextPageLink" onclick='return showDiv("page_20");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> </div><!-- page_19 div -->