
	Where results make sense

Topic: Forearc

In the News (Mon 28 Dec 09)

Northern Trust

Marvin Harrison

Peter Chernin

Gary Locke

Match Play

Penelope Cruz

Mickey Rourke

AR Rahman

Danny Boyle

Hugh Jackman

	Bathymetry of the Tonga Trench and Forearc: A Map Series
		The bathymetry is illuminated at an azimuth of 0° using a shading magnitude of 0.4 to accentuate the abyssal hill fabric at the bend in the trench.
		This deformation of the forearc due to seamount subduction is distinct from the background, "steady-state" erosion, which is characterized by large-scale subsidence of the entire forearc and a gradual regional tilt towards the trench axis (MacLeod, 1994; Clift and MacLeod, 1999).
		The central forearc, which is inferred to be undergoing "steady-state" subduction erosion, is dominated the most by these features, as evidenced by the many large, trench-parallel scarps, most of which must have accommodated large- scale subsidence of the forearc and a gradual, regional tilt of fault blocks toward the trench axis.
	dusk2.geo.orst.edu /tonga (9452 words)

	394
		Juxtaposed against the remnant forearc basin sequences along thrust faults, the Lichi Melange of the Coastal Range is composed of exotic ophiolite and sedimentary blocks, metric to kilometric in size, and coherent turbidite beds, all embedded in a sheared scaly argillaceous matrix.
		The forearc basin is composed of weakly deformed volcaniclastic turbidites and intercalated cherts that were deposited on a volcanic basement that includes Emsian-age boninitic lavas near the base of the sequence.
		Deep-sea sediments with abundant arc-derived volcanic materials are quickly accreted from the Izu forearc side to the Honshu forearc on the Boso triple junction in NW Pacific during Miocene to Pliocene (Ogawa et al., 1989).
	www.the-conference.com /JConfAbs/4/394.html (12638 words)

	Forearc - Wikipedia, the free encyclopedia
		A forearc is a depression in the sea floor located between a subduction zone and an associated volcanic arc.
		It is typically filled with sediments from the adjacent landmass and the island arc in addition to trapped oceanic crustal material.
		The oceanic crustal fragments may be obducted as ophiolites onto the continent during terrane accretion.
	en.wikipedia.org /wiki/Forearc (119 words)

	Oceanic trench - Wikipedia, the free encyclopedia
		Forearcs have the lowest heatflow from the interior Earth because there is no asthenosphere (convecting mantle) between the forearc lithosphere and the cold subducting plate.
		The forearc consists of igneous and metamorphic crust, and this crust acts as buttress to a growing accretionary prism (sediments scraped off the downgoing plate onto the inner trench wall, depending on how much sediment is supplied to the trench.
		The average forearc is underrun by a solid volume of oceanic sediment that is 400 m thick.
	en.wikipedia.org /wiki/Oceanic_trench (3739 words)

	Incipient continental collision and plate-boundary curvature: Late Pliocene-Holocene transtensional Hellenic forearc, ...
		Forearc regions display a wide range of kinematic behaviours, including plate boundary-parallel translation or rotation of rigid blocks as well as deformation internal to the forearc blocks (e.g.
		Increasing boundary curvature was induced by an outward migration of the convergent plate boundary that increased the obliquity of plate-convergence vectors with coeval boundary-parallel lengthening of the forearc.
		The subaerially exposed forearc of the Aegean platelet is a kinematic recorder of the combined effects of plate-boundary migration, expansion of the overriding platelet, changing obliquity of plate convergence and imminent continental collision.
	www.findarticles.com /p/articles/mi_qa3721/is_200303/ai_n9232720 (776 words)

	Untitled Document
		Emplacement of this forearc on a continental margin would be expected to reduce the amplitude of the high, because of the presence of lighter and thicker crust on the downgoing plate, but not to eliminate it altogether.
		Apart from the presence of boninites, the significance of the Bonin forearc as a model for a pre-emplacement ophiolite lies in the spatial relationships that it emphasises.
		During the rifting phase, the volcanic arc of the collided terrane (the NBFA Terrane) is assumed to have separated from the forearc, which remained attached to the New Guinea margin as the PUB and Marum complexes.
	www.es.ucl.ac.uk /people/milsom/ophio.htm (4479 words)

	Evolution of the Aleutian Forearc
		The easternmost Aleutians is the representative region for deformation of the forearc.
		Second, according to convention, the south limb of the forearc basin of the central Aleutians is produced entirely by underplating, whereas according to concepts presented herewith (Sections 3 and 4), this limb of the shelf-basin is produced as the Pacific plate carries the forearc shelf downward toward the mantle.
		Because the trench fill of the model of continuous transport is buried by the propagating forearc, the age of the oldest layers beneath the north wall relate to the rate of propagation of the forearc oceanward, not to the rate of underthrusting as for SPT and discontinuous transport.
	www.mandala.net /murdock/murdock.htm (11693 words)

	SUMATRA GRAVITY
		However, gradients tend to be steep at the coasts in the forearc region, partly because of the change from free-air gravity, which is strongly correlated with local bathymetry, to Bouguer gravity, which is corrected for local topography.
		The yellow line crossing the forearc basin near the equator marks the location of the interpreted profile of Figure 3.6The fl outlines enclosing the letters 'O' and 'B' respectively indicate the locations of the gravity surveys of the Ombilin and Bengkulu basins shown in Figures 3.3 and 3.4 respectively.
		The crest of the forearc ridge is marked by a prominent asymmetric high, with the steeper gradients towards the forearc basin.
	www.es.ucl.ac.uk /people/milsom/SMTRAGRV.htm (5821 words)

	NGDC/WDC for MGG Seafloor Series Volume 2-Core data from the ODP legs 101-129
		The basalt is an island-arc tholeiite characterized by enrichment in large-lithophile elements relative to high-field-strength elements, similar to the submarine lavas of the southern arc seamounts.
		Serpentinite muds recovered from the summit of Conical Seamount are fluid-rich and devoid of texture, whereas muds recovered from the flank of this seamount display plastic, convolute folding and repeated shearing, indicating that the low-density (buoyant) serpentinite mud and its entrained clasts rose to the surface at the center of the seamount.
		The forearc fluids that convert peridotite to serpentinite at Conical Seamount may originate as circulating seawater or as water driven off the oceanic basement and its sedimentary cover as they are subducted; both sources are probably operating although deeper-source water dominate, carrying high concentrations of hydrocarbons, carbon dioxide, and sulfur.
	www.ngdc.noaa.gov /mgg/geology/odp/data/125/odp125.htm (958 words)

	alaska (Site not responding. Last check: 2007-10-10)
		In addition we have studied mechanisms of melange formation, and modeled why certain periods of accretion along the margin were dominated by the formation of melanges, and other times by the accretion of coherent flysch terranes.
		Forearc regions are normally relatively "cold" places under tectonic compression, yet a few contemporary forearc accretionary prisms contain numerous enigmatic granitoid intrusions.
		Ridge subduction has been invoked to explain the presence of near-trench magmas in several forearc regions, as well as anomalous deformation, thermal signatures, and landward structural vergence in accretionary prisms.
	www.eas.slu.edu /People/TMKusky/alaska.html (1882 words)

	DISCUSSION
		Serpentinites in the IBM forearc setting have distinctive structural and compositional characteristics that reflect the dynamic nature of formation of the edifice and the unusual composition of the fluids that are the source of the serpentinization of the protoliths.
		The outer 50 km of the Izu-Bonin forearc is a ridge of variably serpentinized peridotite (Taylor, 1992; Taira et al., 1998; Takahashi et al., 1998; Sato et al., 2004; Kamimura et al., 2002).
		There is a suggestion that the low-velocity zone beneath the outer forearc, which on MCS profiles extends downdip along the base of the forearc wedge, may represent the source of the serpentinized peridotite that rises to form the Izu-Bonin serpentinite seamounts.
	www-odp.tamu.edu /publications/195_SR/synth1/synth1_8.htm (2406 words)

	[No title]
		A close spatial coincidence exists between the Cenozoic structural and topographic basins of the Puget Lowlands and Straight of Georgia and the epicenters of earthquakes that represent active normal faulting in the underlying Juan de Fuca (JdF) slab at depths of 30-70 km.
		Figure 1: Schematic diagram of a possible mechanism of forearc basin subsidence caused by basal forearc tectonic erosion associated with active normal faulting in the underlying slab.
		Forearc detachment and transport occurs with slab descent and results in flexure of the overlying forearc, producing, in turn, subsidence above the region of active normal faulting in the underlying slab, as observed.
	erp-web.er.usgs.gov /reports/annsum/vol37/pt/kirby.htm (993 words)

	Multi-Channel Seismic Images of the Mariana Forearc: EW0202 Initial Results (Site not responding. Last check: 2007-10-10)
		Beneath the forearc, in the southern transects near Saipan, the subducting slab is imaged to a distance of 50-60 km arcward.
		Deep horizontal reflectors (likely original forearc crust) are imaged under the flanks of some of these seamounts.
		Furthermore, MCS data has revealed that some forearc highs previously thought to be fault blocks are in actuality mud volcanoes.
	www.geo.ua.edu /AMG/Mariana_oakleyF2002.htm (376 words)

	Saito (1991b) (Site not responding. Last check: 2007-10-10)
		Structural characteristics of Recent forearc regions can be divided into three types (shelf type, terrace type, and slope type) in terms of the morphology of forearc basins and the topography of basements.
		Sediments from forearc basin can reconstruct the subsidence rate of forearc basin and the vertical movement of island arc and by use of plamktonic microfossils and benthic foraminifera which determine the change in sedimentation rate and paleobathymetry.
		Thus, forearc basins are tectonic recorder to estimate the arc evolution and the change in subduction styles.
	www.ldeo.columbia.edu /~saito/pub/s91b.html (166 words)

	Peridotites from the Izu-Bonin-Mariana Forearc (ODP Leg 125): Evidence for Mantle Melting and Melt-Mantle Interaction ... (Site not responding. Last check: 2007-10-10)
		The results thus indicate that the forearc is underlain by at least two types of mantle lithosphere, one being trapped or accreted oceanic lithosphere, the other being lithosphere formed by subduction-related melting.
		Bathymetric, seismic, dredging and submersible studies of the Izu-Bonin (Ogasawara)-Mariana forearc between the outer-arc high and the trench axis have led to the identification of a series of serpentinite seamounts where mantle peridotite is exposed on the seafloor (Bloomer, 1983; Bloomer and Hawkins, 1983; Taylor and Smoot, 1984; Ishii, 1985; Fryer and Fryer, 1987).
		In contrast to Conical Seamount, Torishima Forearc Seamount is not actively venting fluids and is not therefore at present undergoing hydration from the underlying subduction zone.
	library.iem.ac.ru /j-petr/9-3998/html/egb061_gml.html (13357 words)

	GSA Penrose Conference Report - Lessons in Tectonics, Climate, and Eustasy from the Stratigraphic Record in Arc ...
		This is because trenchward basins are usually too tectonically disrupted by the collision itself to form continuous records and are often separated from the source volcanoes by forearc topography, instead being filled by reworking of older arc sediments.
		Conversely, those parts of the forearc closest to the arc are subject to episodic slumping and mass wasting, preventing formation of continuous sequences.
		Further surveying and drilling of modern forearcs are needed if the optimal location of continuous forearc records is to be better defined for the general case.
	www.geosociety.org /penrose/05pcrpt2.htm (1530 words)

	Project Profiles: Megan Anderson
		The Puget Lowland is located in the Cascadia forearc of Washington, situated between the subduction zone accretionary wedge complex (Olympic Mountains) to the west and the associated volcanic arc to the east (fig.
		Forearc rotation may be caused by the oblique subduction of the Juan de Fuca plate, northward movement of the Sierra Nevada block, and/or Basin and Range extension.
		Recent GPS and seismicity studies show that the forearc continues to rotate and translate northward at 3 to 7 mm/yr.
	geology.usgs.gov /postdoc/profiles/anderson_megan.html (965 words)

	Forearc Basin Evolution Along Accretionary Convergent Margins, Wrangell Mountains, Alaska
		he Wrangell Mountains basin is a Mesozoic forearc basin that developed during a period of accretionary tectonics in the northwestern Cordillera.
		The Wrangell Mountains are an excellent place to study forearc basin development because the thick section of Mesozoic strata has been uplifted and is well exposed, structural and metamorphic deformation has been minimal, and a chronostratigraphic framework exists for most of the basin deposits.
		Does the composition of sandstones and conglomerates in the Wrangell Mountains basin record growth and erosion of volcanic arcs, uplift of subduction complexes, and accretion of allochthonous terranes?
	www.purdue.edu /eas/basin/wrangell_mtns.html (309 words)

	CiteULike: Release of mantle helium from forearc region of the Southwest Japan arc (Site not responding. Last check: 2007-10-10)
		Release of mantle helium from forearc region of the Southwest Japan arc
		Shikoku, Japan, is an island located on the forearc region of the western sector of the Southwest (SW) Japan arc that was formed by subduction of the Philippine Sea plate beneath the Eurasian plate.
		This fact indicates that fluids liberated from the slab in the forearc region cause deep tremors and fracturing within the crust, thereby easing the transfer of fluids to the surface that are mixed with mantle helium to the surface.
	www.citeulike.org /user/tak_echigo/article/681272 (494 words)

	Caribbean --- Coastal and Marine Geology Program - U.S. Geological Survey - Stress
		Strike-slip faults in the forearc region of a subduction zone often present significant seismic hazard because of their proximity to population centers.
		A significant contribution to Coulomb stress increase on strike-slip faults in the back region of the forearc comes from “unclamping” of the fault, i.e., reduction in normal stress due to thrust motion on the subduction interface.
		We argue that although Coulomb stress changes from individual subduction earthquakes are ephemeral, their cumulative effects on the pattern of lithosphere deformation in the forearc region are significant.
	woodshole.er.usgs.gov /project-pages/caribbean/stress.html (467 words)

	[No title] (Site not responding. Last check: 2007-10-10)
		Strike slip faults in the forearc often present significant seismic hazard because of their proximity to population centers.
		Significant contribution to the stress change on strike slip faults in the forearc comes from "unclamping" of the fault (reduction in normal stress) due to thrust motion on the subduction interface.
		The jump from a strike-slip fault near the trench in the Puerto Rico segment to an inland fault in Hispaniola is explained by different stress distributions in the forearc of the two segments due to the change from oblique slip on the subduction interface in Puerto Rico to dip slip in Hispaniola.
	woodshole.er.usgs.gov /bibliographies/current4/4023.html (500 words)

	Bulletins from HMS Scott
		During the survey, we have visited the main sections of the subduction zone forearc, including the plate boundary and accretionary wedge, the forearc high and forearc basin.
		The survey was continued to the upper parts of the accretionary wedge along the majority of the region, and the margins of the forearc (Aceh) basin were covered.
		Following the transit back from the forearc basin, we have picked up the survey of the upper part of the accretionary wedge, which will continue in two blocks until we leave the area.
	nctr.pmel.noaa.gov /indo20041226/hms_scott.htm (2527 words)

	Banda forearc structure (via CobWeb/3.1 planetlab2.isi.jhu.edu) (Site not responding. Last check: 2007-10-10)
		Below I outline a simple structural model for the Banda forearc, which suggests prospective structures of the type found in Seram are likely to occur in the other main island groups around the arc.
		In these interpretations the various metamorphic complexes of Timor and the other Banda forearc islands were seen as allochthonous bodies, in post-plate tectonic interpretations derived from the Asiatic side of the plate boundary.
		I suggest that this structural segmentation of the Banda forearc into zones of greater and lesser basement-involved thrusting was controlled by structural segmentation of the pre-collisional Australian continental margin (see Charlton, 2004).
	www.manson.demon.co.uk.cob-web.org:8888 /bandaforearcstru.html (1531 words)

	Fluid-mobile Element Systematics of Ultramafic Xenoliths from the Izu-Bonin-Mariana Forearc:Implications for the ... (Site not responding. Last check: 2007-10-10)
		The elements enriched in the Hole 779A serpentinites seem exclusively to be from the suite of "fluid-mobile" elements, all of which show abundance variations in arc volcanic rocks and subduction complex metamorphic massifs that are strongly related to slab temperature.
		The observed elemental enrichments in the Mariana Forearc serpentinites (B ~ 17 ppm, Cs ~ 0.14 ppm, Rb ~ 0.33 ppm, Li ~ 3.5 ppm, and Pb ~ O.16 ppm, all highly elevated relative to normal mantle values) demonstrate that these elements are not efficiently subducted to the depths of the volcanic roots beneath arcs.
		Especially for the fluid-mobile elements it is impossible to model the chemical cycle of subduction zones without accounting for potentially large forearc elemental fluxes.
	chuma.cas.usf.edu /~ryan/Ivanserps.html (357 words)

	An inverted continental Moho and serpentinization of the forearc mantle : Nature
		An inverted continental Moho and serpentinization of the forearc mantle
		We find very low shear-wave velocities in the cold forearc mantle indicated by the exceptional occurrence of an 'inverted' continental Moho, which reverts to normal polarity seaward of the Cascade arc.
		This serpentinized material is thought to have low strength and may therefore control the down-dip rupture limit of great thrust earthquakes, as well as the nature of large-scale flow in the mantle wedge.
	www.nature.com /doifinder/10.1038/417536a (323 words)

	NicLakes
		Oblique subduction along the Pacific margin of Central America causes the forearc terrane to move slowly northwest, parallel to the margin and the volcanic arc.
		Geodetic, earthquake, and geologic structure analyses all indicate that oblique convergence is commonly partitioned into an arc-normal component, accommodated by interactions of the subducting plate and the forearc, and an arc-parallel component, which may be absorbed by deformation in the forearc, backarc, or concentrated along the arc.
		While the forearc sliver model is widely supported in the Sumatran and Kuril arcs, interpretations of the Aleutian arc have supported the block rotational model.
	www.ig.utexas.edu /research/projects/NicLakes/index.htm (1068 words)

	Panga Science Plan
		Long-term permanent deformation and seismicity of the convergent margin may extend far into the continent - by building mountain ranges through accretion, or dismembering continents through backarc spreading and migration of forearc slivers.
		The magmatic arc transfers mass and energy to the continent and plays an important role in accommodating tectonic strain in the upper plate.
		In some great earthquakes, seismic slip is concentrated beneath the forearc basins.
	www.geodesy.cwu.edu /community/science_plan.html (917 words)

Try your search on: Qwika (all wikis)