The Neogene tectonics of the central Mediterranean are related to the subduction and trench rollback of the Ionian basin under Eurasia, causing the opening of the Liguro-Provencal and Tyrrhenian back-arc basins and the formation of the Calabrian accretionary wedge. The Calabrian accretionary wedge is a partially ...
NASA Astrophysics Data System (ADS)
Subduction accretion and repeated terrane collision shaped the Alaskan convergent margin. The Yakutat Terrane is currently colliding with the continental margin below the central Gulf of Alaska. During the Neogene the terrane's western part was subducted after which a sediment wedge accreted along the northeast Aleutian Trench. This wedge incorporates ...
extended northward beneath the Okinawa back-arc basin. If we examine the Ryukyu accretionary wedge1 Oblique subduction of the Gagua Ridge beneath the Ryukyu accretionary wedge system Insights from of plate convergence, slip partitioning occurs within the Ryukyu accretionary ...
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against the cohesive wedge (Figure 3a). Some minor back thrusts, related to the growth of the accretionary beneath the rear part of the accretionary wedge (Figure 3e). The old back thrusts, now located above of the experiment and are associated with the growth of the accretionary ...
The Makran accretionary prism is regarded as one of the most extensive subduction complex on Earth. It provides an ideal example of accretionary prism to study processes related to subduction at plate boundaries such as frontal accretion and underplating. The rear portion of the wedge is uplifted and extended by ...
Seismic data, supplemented by field observations, indicate the presence of an accretionary complex in the frontal part of the Gibraltar arc. The complex can be subdivided into an inner complex represented by the classical Flysch units, and an outer complex made up by the Guadalquivir allochthonous units in the Betics and the Preifaine Nappe in the Rif. The ...
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Seismic data offshore and onshore northwestern Morocco (i.e. Atlantic margin, Rharb Basin, Rif foothills) provided a detailed picture of the Western Rif Cordillera. The most external units of the folded-belt consist of allochthonous Cretaceous and Neogene strongly deformed sediments that constitute a westward-directed accretionary wedge. The structure of ...
In this study, the mechanics of forearc basins will be the object of a numerical investigation to understand the relationships between the wedge deformation and forearc basin formation. The aim of this work is to gain insight into the dynamics of the formation of the forearc basin on top of a deforming accretionary wedge, including the ...
We investigate the deformation of orogenic wedges that form in the early stages of continent-continent collisions using a two-dimensional numerical model limited to the upper lithosphere. Our models show that deformation at the plate margins is influenced by rheology, surface processes, and the balance between inward mass flux and outward subduction flux, as controlled by the ...
Controls on accretion of flysch and m�lange terranes at convergent margins are poorly understood. Southern Alaska's Chugach terrane forms the outboard accretionary margin of the Wrangellia composite terrane, and consists of two major lithotectonic units, including Triassic-Cretaceous m�lange of the McHugh Complex and Late Cretaceous flysch of the Valdez Group. The contact ...
This paper presents magnetic fabric analysis to examine the internal structure of the accretionary prism toe in the Nankai Trough, off the east coast of Japan. Two sites (C0006 and C0007) drilled during Integrated Ocean Drilling Program (IODP) Expedition 316 penetrated the sediment section, including intra wedge thrusts and the frontal ...
The Cascadia convergent margin is a first-order research target to study the impact of rapid sedimentation processes on the mechanics of frontal subduction zone accretion. The near-trench part of the accretionary prism offshore Washington is affected by strongly increased glacial age sedimentation and fan formation that led to an outstanding Quaternary ...
The southernmost tip of South America is an active continental margin where oblique convergence between plates, transcurrent motion, and tectonic rotation on land make the geodynamic setting more complex than that of the central Andes. A multichannel seismic data set has been used in conjunction with multibeam and altimetry data to clarify the regional architecture of the continental margin from ...
360� borehole resistivity images at Leg 196 (Nankai prism) were used to assess deformation. Deformation was indicative of basinal compaction at the reference site 1173 and concentrated in discrete zones at Site 808 (toe of wedge), including the frontal thrust and the d�collement. Fractures in the upper part of the accretionary ...
Detrital sedimentary records include vast archives of material that have been removed from developing tectonically active regions. These archives have been used to investigate challenging questions on continental deformation, exhumation and palaeodrainage using a variety of different techniques including heavy minerals, fission-track dating and palaeocurrent reconstructions. The Hengchun Peninsula ...
Understanding the controls on uplift, exhumation and topography in orogenesis requires integrating the effects of both climatic and tectonic forcing. The potential for climatic forcing of individual structural units within thrust wedges has recently been hotly debated and tested. Here we use a recently developed discrete element model (Naylor et al., 2005) to analyse the ...
Sandbox models of accretionary wedges have demonstrated that fault systems grow episodically via cycles of alternating wedge thickening, which is accommodated by slip along faults within the wedge (underthrusting), and wedge lengthening, which is accommodated by growth of new faults at the ...
There is considerable evidence now that over the last 15 m.y., the Cascadia subduction wedge along the Olympic Peninsula has been in a flux steady state, where the accretionary influx is balanced with the erosional outflux from the forearc high. This steady state condition implies that the size and shape of the wedge have also been in ...
Stage 1 of the Nantroseize project extended from the trench to the Kumano forearc basin and succeeded in drilling and coring the frontal thrust, a major splay fault, the forearc basin and the older wedge. The first approach we use is to combine LWD resistivity, moisture and density data, and other properties (physical and physico-chemical) obtained on core ...
Ample evidence suggests that the shallowest segment of subduction interface, down to a few km depth and updip of the megathrust seismogenic zone, exhibits a velocity-strengthening (aseismic) behavior. According to the dynamic Coulomb wedge model, it is mainly this coseismic strengthening that is responsible for the growth and permanent deformation of the overlying ...
of thick basin sediments. Back- thrusting in the form of tectonic wedging has been identified along. The gravity anomaly can be modeled with a continuous west-dipping back stop extending under the tectonic wedge rates in the back thrust domain, west of the tectonic wedge, prior to collision. We have mapped fault
The Gulf of Cadiz lies offshore of Southwest Iberia and Northwest Morocco where the famous Lisbon earthquake and tsunami struck in 1755. Here the plate boundary between Africa and Eurasia is complex, marked by a broad region of deformation spanning about 200 km in a north-south direction. Structurally, the Gulf of Cadiz is the presence of a thick tectonically deformed sedimentary ...
A self-consistent theory for the mechanics of thin-skinned accretionary Coulomb wedges is developed and applied to the active fold-and-thrust belt of western Taiwan. The state of stress everywhere within a critical wedge is determined by solving the static equilibrium equations subject to the appropriate boundary conditions. The ...
Subduction zones account for 90% of global seismic moment release, generating damaging earthquakes and tsunamis, with potentially disastrous effects on heavily populated coastal areas. Understanding the processes that govern the strength of earthquakes, and nature and distribution of slip along these plate boundary fault systems, are crucial steps toward evaluating and mitigating geohazards, ...
Upper Messinian conglomerates in Calabria, southern Italy: Response to orogenic wedge adjustment as a result of the Messinian base-level falls. Along the Ionian coast of Calabria, southern Italy, these rocks part of the Cala- brian accretionary wedge. We propose that the upper Messinian deposits were produced
It is easily shown that many well-imaged accretionary wedges are mechanically heterogeneous based on spatial variations in wedge taper. For example, the toes of active accretionary wedges such as the Nankai trough and Barbados display deceasing surface slope ? away from the toe, with no ...
sequence of evaporites further back in the WMR (the site of the pre-Messinian wedge). The lack of imper 19 November 2001 Abstract Sandbox experiments of accretionary wedges were performed incorporating a thin weak layer of micro glass beads. The impact of heterogeneous sedimentary input on wedge mechanics
is controlled by the distance between the two back-thrusts in the up- per wedge, that this upper basin formed in Fig. 4: the original foredeep sedimentary wedge (first stage) is incorporated and tilted by a back-propagating accretionary wedge there may form back-thrusts. When associated to a basal decollement, a ...
The presence of different subduction modes in the convergence process between the Nazca and South-American plates along the Chilean margin is known from previous investigations. In order to study this variability in detail a comprehensive combined off- and onshore geo-scientific survey (SPOC) was recently conducted between Coquimbo and Valdivia in collaboration between a number of German and ...
Among the seismic surveys carried out in the framework of the EU - THALES WAS RIGHT project in the Lesser Antilles subduction zone, the SISMANTILLES II cruise of N/O ATALANTE (IFREMER, PI M. Laigle) collected 3 375 km of multi-channel reflection seismics with its 4.5 km long, 360 channels streamer. This survey focuses on the updip portion of the contact zone between the forearc and oceanic ...
As part of the NanTroSEIZE Project (IODP Expeditions 315 and 316), the clay mineral assemblages from 689 samples of hemipelagic mud were characterized by X-ray diffraction. We used oriented aggregates of clay-size fractions to estimate the relative percentages of smectite, illite, chlorite, kaolinite, and quartz. The saddle/peak method was used to show the bulk character of illite/smectite mixed ...
The nature of active deformation in the Gulf of Cadiz is important for developing a better understanding of the interplate tectonics and for revealing the source of the 1755 Great Lisbon earthquake. New, high-resolution 3-D seismic data reveal a classic pull-apart basin that has formed on an east striking fault in the Southern Lobe of the Gulf of Cadiz accretionary ...
One of unsolved problems in subduction zone is what controls the up-dip limit of seismogenic zone. Several hypotheses have been proposed; 1) change in friction behavior from stable to unstable slip of clay minerals caused by thermally controlled transformation (Hyndmann et al., 1993), 2) increase of effective strength due to reduction of fluid pressure caused by decrease in dehydration rate of ...
COCORP deep seismic reflection profiles across the Ouachita Mountains in western Arkansas suggest that a large fraction of the crust in this region is composed of tectonically thickened Paleozoic sediments (and metasediments). Reflections representing a southward-thickening wedge of layered rock on the northern portions of the survey are associated with approximately 12 km ...
Orogenic wedges are standard elements of collisional plate tectonics, from accretionary prisms to retro-arc basins. Recent study of orogenic wedge development has focused on links between mechanisms of internal deformation and surface processes. Models of orogenic wedges are commonly presented in the cross-section ...
... of the sequence. Comminuted remains of barnacles and cementing bivalves become more common proximal to the largest ... accretionary wedge onlaps the basement beneath the bonebed. Cementing Ostrea sp. also...
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The growth of accretionary wedges along subducting plate margins has inspired generations of sandbox experiments. These experiments typically contract sand layers to simulate the deformation of sedimentary rocks as the wedge grows in width and height. In the absence of erosional processes, the ratio of wedge ...
Landward vergence in accretionary wedges is an uncommon phenomenon not readily explained by classical Mohr-Coulomb critical wedge theory. Predominantly landward- vergent thrust faults are observed along the Cascadia convergent margin from 45�N to 48�N. We present depth-migrated multichannel seismic images of the internal structure ...
High tibial osteotomy (HTO) is a procedure for treating medial compartment osteoarthritis (OA) of the varus deformed knee. Frontal and sagittal alignment after closed- and open-wedge HTO were compared radiologically in a matched-pair study. The mean intra-operative frontal plane correction (FT axis) was +7.5 degrees for ...
PubMed
The 27 February, 2010 Maule earthquake (Mw = 8.8) ruptured ~ 400 km of the Nazca-South America plate boundary and caused hundreds of fatalities and billions of dollars in material losses. Here we present constraints on the fore-arc structure and subduction zone of the rupture area derived from seismic refraction and wide-angle data. The results show a wedge shaped body ~ 40 km ...
Many well-imaged accretionary wedges are mechanically heterogeneous based on spatial variations in wedge taper. For example, the toes of active accretionary wedges such as the Nankai trough and Barbados display deceasing surface slope ? away from the toe, with no associated variation in the ...
We propose a new model for the evolution of accreting wedges at retreating subduction zones. Advance and retreat refer to the polarity of the velocity of the overriding plate with respect to subduction zone. Advance indicates a velocity toward the subduction zone (e.g., Andes) and retreat, away from the subduction zone (e.g. Apennines, Crete). The tectonic mode of a subduction ...
Mud volcanism is a global phenomenon in mostly convergent margin settings, whose nature has long been subject to scientific investigation. However, only recently its significance has been unravelled by quantitative studies in well-investigated submarine environments, like large accretionary complexes. The fluid flux through active mud volcanoes has been estimated to exceed ...
We report an uplift of 5 m with a horizontal displacement of more than 60 m due to the 2011 Tohoku-Oki earthquake. The uplift was measured by an ocean-bottom pressure gauge installed before the earthquake on a frontal wedge, which formed an uplift system near the Japan Trench. Horizontal displacements of the frontal ...
As far as we can ascertain the only way of increasing the permeability parallel to shear zones developed in muds is to dilate them so that pore diameter r increases in conjuction to any grain alignment decrease in the value of T(sub x) Karig (1990) likewise suggested that dilational paths are necessary to account for the observed properties and fabrics in the decollements of an ...
... to the postorbital process of the frontal. The lacrimal contributes to the lateral border of the antorbital notch. Laterally the lacrimal wedges between the overlying maxilla and the underlying ... ...
The recent Haiti earthquake, although it ruptured dramatically the strike-slip Enriquillo Plantain Garden Fault Zone (EPGFZ), is actually located where this fault cross-cut or is overlapped by the frontal part of the Trans-Haitian belt accretionary wedge. This belt started accreting flysch series in the North of Hispaniola during the ...
The early stages of subduction-related deformation at Nankai Trough and Costa Rica convergent margins have been central objectives of recent deep-ocean drilling. The oceanic sediment input at these two margins differs considerably: at Nankai silty clays are dominant overlain by a thick turbiditic cover (total thickness ~700 m), while Costa Rica has a thick incoming section of carbonaceous ooze ...
Along the Cascadia margin offshore Oregon, the structural vergence at the toe of the accretionary wedge varies from landward vergent offshore northern Oregon to seaward vergent across the southern Oregon margin. A transition zone between these vergence domains occurs along the central Oregon portion of the wedge, centered on the ...
In August 2008, a research expedition was conducted on the n. Cascadia margin by the Geological Survey of Canada (GSC) as part of the Earth Science Sector, Natural Gas Hydrate Program, Natural Resources Canada (NRCan). This collaboration included researchers from several universities as well as Canadian and U.S. government agencies. The primary objective was to determine the impact of gas hydrate ...
The dynamic processes leading to synconvergent exhumation of high-pressure low-temperature (HP-LT) rocks at oceanic accretionary margins, as well as the mechanisms maintaining nearly steady state regime in most accretion prisms, remain poorly understood. The present study aims at getting better constraints on the rheology, thermal conductivity, and chemical properties of the ...
The Ashuanipi complex is one of the largest massif granulite terrains of the Canadian Shield. It makes up the eastern end of the 2000 km long, lower-grade, east-west belts of the Archean Superior Province, permitting lithological, age and tectonic correlation. Numerous lithological, geochemical and metamorphic similarities to south Indian granulites suggest common processes and invite comparison ...
Pore fluid pressures in subduction zones are a primary control on fault strength and slip dynamics. Numerous studies document elevated pore pressures in the outer wedge along several margins. Seismic observations and the occurrence of non-volcanic tremor provide additional evidence for the presence of near-lithostatic pore pressures at the plate interface far down-dip from the ...
Accreting margins often display an outer thrust and fold belt and an inner forearc domain overlying the subduction plate. Assuming that this overlying material behaves as Coulomb material, the outer wedge and the inner wedge are classically approximated as a critical state and a stable state Coulomb wedge, respectively. Critical ...
The Nankai Trough, Japan near Kumano Basin displays a well developed accretionary prism with a major out-of-sequence �megasplay� thrust separating the recently active outer wedge of the prism from the forearc basin deposits. While not in the seismogenic zone, this thrust is thought to play a key role in tsunamigenesis by transferring deeper coseismic ...
Accretionary wedges have been an important research target from view points of earthquake mechanism at the subduction zone, sediment deformation that is closely coupled with hydrology, and resource exploration such as methane hydrates. The knowledge obtained from the study may also be useful for site selection of geological disposal of hazardous materials ...
We present here a comparison of the tectonic evolution of subduction wedges at the Cordilleran margin, as represented by the Franciscan wedge of northern California and the Cascadia wedge in the Olympic Mountains, Washington State. We use a geodynamic model to illustrate the growth and morphological evolution of these ...
Using a new implementation of critical taper wedge mechanics, we investigate the relationship between structural styles and calculated mechanical strength properties in two unique fold and thrust belts. Through the analysis of regional seismic reflection profiles and detailed bathymetric data, we define the wedge taper geometry of the fold and thrust belts ...
A three-dimensional prestack depth-migrated seismic reflection data volume acquired off Shikoku Island, Japan covers the seaward portion of the Nankai Trough accretionary prism. We calculate and interpret total horizontal shortening lengths along three cross-sectional profiles through the volume, incorporating a technique addressing the significant amount of water volume ...
primarily at the places where young lithosphere has almost no strength, between plates diverging by shearing within a wedge. The shearing and imbrication of the cool, wet, forward parts of accretionary of Columbia University. Figure 6. Depth-converted seismic-reflection and velocity profiles across Nankai
Several aspects of the mechanics of convergent margins are investigated. A quantitative model for the mechanics of thin skinned deformation in accretionary wedges and thrust belts, and a test of plate driving forces, including those at convergence zones, against the absolute velocities of the plates since the late Cretaceous are presented. Constraints are ...
. Orogenic andesites and plate tectonics. Springer Verlag, Berlin, Heidelberg, New- York. GILLJ. B., SEALES C of upper plate material losses caused by tectonic erosion. Jolournal of Geo- physical Research 97, 217. & MALAVIEILLEJ. 1994. Coulomb theory applied to accretionary wedges - Possible causes for tectonic erosion and
Recent studies of convergent plate margins and the structural development of forearc terranes are summarized in a critical review of U.S. research from the period 1987-1990. Topics addressed include the geometry of accretionary prisms (Coulomb wedge taper and vertical motion in response to tectonic processes), offscraping vs underplating or subduction, the ...
The well-known model for the critical taper of an accretionary wedge includes overpressure as a first-order parameter. Fluid overpressures reduce frictional resistance at the base of a wedge but they also act as body forces on all material particles of the wedge, in addition to that of gravity. By means of sandbox ...
Electrical images recorded with Resistivity-At-Bit (RAB) from two sites drilled during Ocean Drilling Program (ODP) Leg 196 were analyzed to study the effects of subduction at the Nankai margin. For the first time in the history of scientific deep-sea drilling in ODP, in situ complete borehole images of the d�collement zone were obtained. Analyses of all drilling-induced fracture data indicated ...
Using high-resolution seismic profiles and other geophysical data, collected during R/V Meteor Cruise M74/2, we investigate the distribution patterns of shallow sediments, their structure and deformation processes, and their role in the migration, accumulation and seepage of hydrocarbon-rich fluids. Here, we show that rapid syn-kinematic sedimentation at the frontal Makran ...
Landward-dipping seismic reflectors (LDRs) within the accretionary wedge at convergent plate margins have generally been interpreted as tilted-bedding or thrust-fault surfaces (e.g., Mexico, northern Japan). This interpretation accords with models in which trench-axis sediments are scraped off the descending plate to form a series of imbricate thrust ...
The transgressive-regressive history of an active margin bordering a marine foreland basin is controlled by the relative rates of sediment supply, basin subsidence, and sea level change. The purpose of this research is to better understand the functional relationships among these factors and shoreline position by exploring solutions to a coupled source-basin numerical model. The model consists of ...
The objective is to capture the 3D failure modes in accretionary wedges and their analogue experiments in the laboratory from the sole knowledge of the material and interface strengths. The proposed methodology relies on the maximum strength theorem inherited from classical limit analysis. The virtual velocity field is constructed by spatial ...
Heat flow from the accretionary wedge that forms the Pacific continental margin of Colombia and southern Panama increases to its maximum value at the toe of the wedge, where it reaches values of up to 120 mW/m2 in the south [4 degrees N] and more than 200 mW/m2 in the north [6.5 degrees N]. Heat flow diminishes landward to about 40 ...
We present the results of structural and stratigraphic interpretations for the multichannel seismic profiles to reveal the structure of the Nankai accretionary wedge off Shikoku Island. On the basis of reflection characteristics we identify three major seismic units that correspond to a unit consisting of both Oligocene-Miocene ...
The Altaids is one of the largest accretionary orogenic collages in the world with the highest rate of Phanerozoic continental growth and significant metallogenic importance. It is widely accepted that subduction-related orogenesis of the Altaids started in the late Precambrian and gradually migrated southward (present coordinates). However, it is uncertain when and how the ...
The Western Pacific Panel of the Ocean Drilling program recommends that the following scientific problems take highest priority for the next round of scientific drilling in the western Pacific region: (1) origin and development of marginal basins, and their implications for the tectonic history of western Pacific arc systems; (2) origin and tectonic history of oceanic forearcs, with implications ...
field in- clude high deformation in the frontal portion of the wedge roughly coinciding with the post-Messinian of the total emitted volume) prisms. Camerlenghi et al. (1995) proposed that the Messinian evaporites prevent increase of mud at the transition between the post-Messinian wedge and pre-Messinian wedge 80 ...
We document the four most important drainage basins of the Iranian Makran and their fluvial terraces to investigate the surface record of the on-going Makran subduction zone. We compare stream profiles extracted from Aster Digital Elevation Model using a slope-area model for the main channel of each catchment. The five studied rivers are transverse and flow from the northern crest line of the ...
During Jurassic-Cretaceous times, the area of the central Apennines was part of a large, Bahamian-type carbonate platform-basin system, whereby the area of the Gran Sasso was situated between the carbonate platform of Latium and the Abruzzi in the west and the deep basinal area of Marche-Umbria to the east. This transitional area experienced 1. Early Jurassic rifting of the Adriatic margin, ...
The Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) is a a long-term effort to image, sample, and instrument the up-dip portion of a subduction megathrust in a location where great earthquakes repeatedly occur. It comprises a series of geophysical surveys, including 3D seismic reflection, a transect of drilled boreholes, and a long-term borehole observatory component. The objective is to ...
Because sediment accretion and basal erosion at subduction zones are modulated by stress changes due to great subduction earthquakes or other episodic events, submarine wedges do not always stay in a critical state but must switch between critical and stable states. For a Coulomb wedge that is in a stable state, the classical critical ...
Timing data on a frontal thrust system indicate that the Sevier thrust wedge of central Utah advanced rapidly to is ultimate structural front in {approximately}30 m.y., between early Albian and Campanian time. It then persisted by out-of-sequence thrusting for an additional 25 m.y., until the early Eocene. The key to the history of the ...
The classical theory of critically tapered Coulomb wedge describes the geometry and state of stress of subduction zone thrust wedges that are averaged over millions of years. We propose a dynamic Coulomb wedge theory to build a link between the long-term process and earthquake cycles. Observations of great earthquakes indicate that ...
Multichannel seismic reflection data, swath mapping morphology and stratigraphic data from an offshore drill site were used to derive a geological model of the Ecuador margin and to examine its along-strike structural variations in relation to the Carnegie Ridge subduction. MCS data were recorded using a 45-L airgun seismic source and a 360-channel streamer. Shots were fired every 50-m, providing ...
Based on an extensive set of swath bathymetry data that was obtained on 12 cruises and cover about 72% of the Chilean continental margin between 33�S and 43�S, up to now more than 60 submarine mass wasting features were detected, mapped and described. They form a wide spectrum in size, apparent slide mechanism and volume. Most of them are small if compared to mass wasting features on passive ...
First ROV diving survey has been conducted around the selected three sites (Formosa Ridge, Sites C and G) in offshore SW Taiwan, where gas hydrate broadly occurs within the thick Quaternary marine sediments. The Formosa Ridge and Site G are located in the South China Sea Continental Slope, whereas Site C is located in the frontal portion of a fault-bend fold in the ...
A compilation of swath bathymetric data from the Ecuador South-Colombia subduction zone allows a detailed characterization of the geomorphology of the trench and margin seafloor. These data are used together with seismic reflection profiles to evaluate the age and the effects of the Carnegie ridge (CR) subduction, and thus determine the modes of mass transfer along the margin. The outer trench ...
At many subduction zones, accretionary complexes form as sediment is off-scraped from the subducting plate. Mechanical models that treat accretionary complexes as critically tapered wedges of sediment demonstrate that pore pressure controls their taper angle by modifying basal and internal shear strength. Here, we combine a numerical ...
We examined in eastern Pennsylvania, New York and Vermont (USA) various types of unmetamorphosed m�langes, which formed at an accretionary wedge-front of the Ordovician Taconic allochthon in the central and northern Appalachian orogenic belt. These m�lange occurrences display structural evidence for progressive deformation of a middle-late Ordovician ...
Seamount sudbuction is a common feature at convergent plate margins and several examples can also be seen at the Nankai wedge, but its impact on methane hydrate accumulation has not fully described. In order to understand the accumulation mechanism of methane hydrate, the key issue would be the fluid flow within the sediments. The fluid flow can be classified into two types; ...
Paleontological and isotopic age data from the Franciscan complex in the Ortigalita Peak quadrangle, Diablo Range, California, provide new insight into the tectonic evolution of at least part of the Franciscan complex. Graywacke, shale, pillowed greenstone, and chert in the quadrangle were deposited in Late Jurassic (Tithonian) time, about 135 to 150 m.y. ago, on the basis of radiolaria. These ...
Characterization of the protoliths of a subduction-accretion complex can provide major insights into the dynamics of the subduction channel. Geochemistry of eclogites found as boulders in a Tertiary conglomerate from the Guajira Peninsula, Colombia, indicate that these rocks are mainly metamorphosed basalts. A negative Nb-anomaly and flat to enriched REE patterns suggest that the eclogite ...
Blueschist facies rocks are an essential element in all discussions related to subduction processes. Some incertitude concerns their depth of burial and subsequent exhumation mechanisms, which should involve tectonic processes sufficiently rapid to preserve mineral phases stable under high pressure - low temperature conditions. It has become crucial to understand and ascertain the thermobarometric ...
The Central Asian Orogenic Belt (CAOB) is the world's largest Paleozoic to Mesozoic accretionary orogen. It is characterized by the occurrence of large amount of juvenile crust. The Altai Mountains in NW China are a type terrane of CAOB. Our new zircon age data, along with the available age information, have established four Paleozoic plutonic events at ca. 460 Ma, 410-400 ...
During subduction at the Franciscan trench beginning at 170-160 Ma and continuing to the present, marine sedimentary and lesser volcanic rocks have been underthrust, accreted, and metamorphosed to form the Franciscan accretionary wedge. The South Fork Mountain Schist (SFMS) forms the eastern margin and structural top of the wedge and ...
The Calabrian Arc (CA) is a subduction system that develops along the African-Eurasian plate boundary in the Ionian Sea and connects the E-W trending Sicilian Maghrebian belt with the NW-SE trending Southern Apennines. The first systematic geophysical investigation in the offshore region of the CA was conducted during the 70's by the Institute of Marine Geology (now ISMAR) with the R/V 'Bannock' ...
Regional structural and stratigraphic relations in the northern California Coast Ranges require an episode of extensional tectonic unroofing of coherent blueschist terranes of the Eastern belt of the Franciscan complex along a crustal-scale, low-angle, normal-fault system, here named the Cost Range detachment. This tectonic unroofing occurred during the latest Cretaceous and early Tertiary, ...
Until recently, the importance of intense sea floor emissions of hydrocarbon-enriched fluids related to the ongoing movement and development of the olistostrome-accretionary wedge complex located in the Gulf of C�diz (Figure la), remained uncertain. The Gulf of C�diz is located in the transitional zone between the Gloria transform fault zone, which is ...
It is becoming apparent that the character of regional hydrate and free-gas distributions in passive-margin environments is different to the equivalent distributions in accretionary wedges at convergent margins. Accretionary wedges typically have widespread BSRs with underlying gas zones of a few tens of metres in ...
In an active margin, the material overlying the subduction plane is often assumed to behave as a Coulomb material. A splay fault may hypothetically be modeled as a weak plane having an effective friction coefficient lower than the internal friction coefficient of the Coulomb material. Accreting margins often display an outer thrust and fold belt, which may be approximated as a critical state ...
Megasplay faults, very long thrust faults that rise from the subduction plate boundary megathrust and intersect the sea floor at the landward edge of the accretionary prism, are thought to play a role in tsunami genesis. We imaged a megasplay thrust system along the Nankai Trough in three dimensions, which allowed us to map the splay fault geometry and its lateral continuity. ...
The Kamchatsky Mts. accretionary complex in the Eastern Kamchatka orogenic belt was studied for identification of the oceanic and suprasubduction components into accretionary wedges. That complex is divided into two tectonic units. The Lower unit is formed sedimentary and tectonic melanges containing arc-related components (Late ...
The objective of ODP Leg 196 was to clarify deformation behavior and fluid flow in the Nankai accretionary prism. Leg 196 was the 3rd deep-sea drilling investigation of the Nankai accretionary prism following Legs 131 and 190. In order to measure the physical properties of the decollement zone, a special method was designed which uses LDW ...
Slope basin sediments in the vicinity of the NanTroSEIZE transect record the recent deformation history of the accretionary prism fold and thrust belt (Fig. 1). 3D seismic imaging of these sediments reveals recent uplift, along-strike extension, and mass-wasting�including an individual mass transport complex >200 meter thick�of a broad region within the outer ...
The objective is to demonstrate that the equilibrium element method (EEM) provides the stress distribution in geometrical models of folds, relevant to fold-and-thrust belts as well as accretionary wedges. The core of the method, inherited from limit analysis, is the search for an optimum stress field that (1) is in equilibrium, (2) remains everywhere below ...
In a recent paper (Eur. J. Mineral. 20), Massonne and Willner (2008) presented P-T pseudosections for common rocks involved in accretionary wedge systems and argued that the dehydration of psammopelitic rocks could be an essential process for the formation of these systems. These authors assumed that this dehydration process leads to softening of the ...
Northern Papua New Guinea and the Solomon Sea are the site of a modern oblique, arc-continent collision, which is progressing from northwest to southeast. By combining offshore seismic data from the Solomon Sea with geologic mapping in the Markham Valley area of northern Papua New Guinea the authors are predicting the outcome of this collision. The Huon Gulf is the present site of initial ...
The Makran Accretionary Prism (MAP) is formed by active convergence between the Eurasian and the Arabian plates. The system is characterized by a shallow slab dip (<2�), great sediment thickness in the Oman Sea and a wedge width of >500 km, >300 km of which are exposed onshore. New mapping results and structural sections document the structural ...
In this study, we used porosity to assess the compaction state of the Nankai accretionary wedge sediments and any implications for stress and pore pressure. However, hydrous minerals affect porosity measurements, and accounting for them is essential toward defining the interstitial porosity truly representative of the compaction state. The water content of ...
We constrain the orientations and magnitudes of in situ stress tensors using borehole wall failures (borehole breakouts and drilling-induced tensile fractures) detected in four vertical boreholes (C0002, C0001, C0004, and C0006 from NW to SE) drilled in the Nankai accretionary wedge. The directions of the maximum horizontal principal stress (SHmax), ...
Seismic reflection data collected over the past 10 years by the Institute for Research on Earth Evolution (IFREE) of Japan Agency for Marine Earth Science and Technology (JAMSTEC) image a zone of complex thrusting at the toe of the Nankai accretionary prism south of Kii Peninsula, Honshu, Japan. The frontal part of the Nankai prism west of Shionomisaki ...
The Archean Khizovaara structure is located within the North Karelian greenstone belt and consists of two metamorphosed complexes. U-Pb isotope dating constrained its formation within a short range of 2.82-2.78 Ga. The older complex comprises metamorphosed tholeiites, boninites, ferrobasalts, and tholeiitic andesites. Such a rock association is typical of the Phanerozoic initial intra-oceanic ...
In this study, the mechanics of forearc basins will be the object of a numerical investigation to understand the relationships between wedge deformation and forearc basin formation. The aim of this work is to gain an insight into the dynamics of the formation of the forearc basin, in particular the mechanism of formation of accommodation space and the preservation of basin ...
The Earth's active convergent margins are characterized by dynamic feedback mechanisms that interact to form an intricate system in which a crustal wedge is shaped and metamorphosed at the will of two large, converging plates. This framework is accompanied by complicated processes, such as seismogenesis and the exhumation of high pressure rocks. To honor the dynamic ...
As part of SEATOS (``Sumatra Earthquake and Tsunami Offshore Survey''), conducted in May 2005 from M/V The Performer, high- resolution seismic reflection profiles were collected over parts of the Sunda accretionary wedge southwest of Sumatra. Most of these single-channel, GI-air gun profiles were sited to investigate subsurface geology associated with ...
We investigate the structure of the accretionary wedge of the Caledonian orogen, the underlying autochthonous/parautochthonous carbonaceous alum shales and the Precambrian basement. We have conducted 60 broad-band magnetotelluric soundings along a 180 km long profile in J�mtland, Sweden, across the eastern section of the Central Scandinavian Caledonides. ...
Three E-W transects of closely spaced heat flow measurements across the Barbados accretionary complex are reported. One transect, shows that heat flow decreases arcward roughly in proportion to the thickening of the wedge over the actively accreting zone. This decrease is due to the combined thermal effects of the underthrusting oceanic lithosphere and ...
BACKGROUND: Lateral wedges reduce the peak knee adduction moment and are advocated for knee osteoarthritis. However some patients demonstrate adverse biomechanical effects with treatment. Clinical management is hampered by lack of knowledge about their mechanism of effect. We evaluated effects of lateral wedges on frontal plane ...
Accretionary wedges and foreland thrust belts exhibit structural associations at their respective deformation fronts that can be grouped in distinct families. At accretionary margins, one style involves major forethrusts with regular spacing and foreland-directed thrust propagation such as at Nankai or Barbados. A contrasting, rather ...
Research on the Sumatra-Andaman earthquake of 2004 has challenged two popular paradigms; that the strongest subduction earthquakes strike in regions of rapid plate convergence and that rupture occurs primarily along the contact between the basement of the overriding plate and the downgoing plate. Subduction zones presenting similar structural and geodynamic characteristics (slow convergence and ...
For a typical two-dimensional (2-D) marine multichannel seismic reflection survey, cross currents cause receiver cable side drift, and data collection becomes a limited swath 3-D survey. Processing of swath marine survey data using standard 2-D imaging procedures can create spurious discontinuities and wipeouts in the images of reflection events. These anomalies are commonly attributed to geology ...
The central segment of the Aleutian Trench (162{degree}W to 175{degree}E) is an intraoceanic subduction zone that contains an anomalously thick sedimentary fill (4 km maximum). The fill is an arcward-thickening and slightly tilted wedge of sediment characterized acoustically by laterally continuous, closely spaced, parallel reflectors. These relations are indicative of ...
Steady state models of overgrowth and vein formation are developed using kinetic data for quartz dissolution and precipitation and estimates of fluid advection, pore-fluid and grain-boundary diffusion. Application of these models to overgrowths and veins in the Kodiak accretionary complex suggests that the Kodiak Formation deformed continuously by a grain-boundary ...
ODP Leg 110 achieved a first-ever penetration of the detachment surface (decollement) between two converging plates. The Barbados forearc is the location of an eight-site transect drilled across this accretionary wedge and on the incoming Atlantic plate. Their results show offscraped sediments form repeated thrust-faulted sequences at the ...
We present the results of a 280km long regional wide-angle seismic profile conducted in the Lesser Antilles. The profile crosses an active island arc, the Tiburon Ridge and one of the largest accretionary complexes in the world. Crustal thickness beneath the island arc is ~25km and 8km beneath the Accretionary Prism suggesting oceanic crust below. We ...
This paper presents results of a seismic tomography experiment carried out on the accretionary margin off southwest Taiwan. In the experiment, a seismic air gun survey was recorded on an array of 30 ocean bottom seismometers (OBS) deployed in the study area. The locations of the OBSs were determined to high accuracy by an inversion based on the shot traveltimes. A ...
Stratigraphic and paleomagnetic studies have suggested that the western Transverse Ranges (WTR) microplate is allochthonous, and may have experienced translational and rotational motions. Present paleocurrent directions from the Upper Cretaceous Jalama Formation of the Santa Ynez Mountains are north-directed; these forearc sediments (Great Valley sequence) contain magmatic arc-derived conglomerate ...
Mud volcanoes have been widely documented in areas of overpressure where explosive expansion of trapped methane has occurred during argillokinesis. In an area with high sedimentation rate, such as the Gulf of Mexico, there may be no time for fine-grained sediment to de-water before being covered by impermeable material. In an accretionary wedge this ...
Subduction zone earthquakes can propagate to the surface causing large seafloor displacements resulting in tsunamis. This requires the earthquake to rupture through clay-rich sediments of the accretionary wedge, which are largely aseismic. As found previously, the frictional properties of a range of wet clays at low slip velocity are velocity ...
P and mode-converted S waves from airgun shots recorded along a line of ocean bottom seismometers were used to construct a 2-D velocity section across the Nankai Trough and the toe of the accretionary complex, offshore southeast Japan. The site was chosen because of plans to drill into the seismogenic zone of the main subduction thrust, which has a history of M ~ 8 ...
Placing ore formation within the overall tectonic framework of an evolving orogenic system provides important constraints for the development of plate tectonic models. Distinct metallogenic associations across the Palaeozoic Lachlan Orogen in SE Australia are interpreted to be the manifestation of interactions between several microplates and three accretionary complexes in an ...
The Falls Lake melange in the eastern Piedmont of North Carolina is composed of mafic and ultramafic blocks and pods of diverse shapes and sizes, from about 1 cm to 7 km in length, dispersed without stratigraphic continuity in a matrix of pelitic schist and metagraywacke. The melange lies between the Carolina slate belt on the west and the Raleigh belt on the east. This terrane has been mapped in ...
The accretionary prism of the Nankai Trough, Japan provides an excellent location to study the kinematics of a fold and thrust belt developed primarily in low permeability units. Recently acquired 3D reflection seismic data covering a 12 x 56 km area from the Kumano basin seaward to the deformation front reveals three structural domains within the frontal ...
Integrated Ocean Drilling Program (IODP) Expedition 316 Sites C0006 and C0007 examined the deformation front of the Nankai accretionary prism offshore the Kii Peninsula, Japan. In the drilling area, the frontal thrust shows unusual behavior as compared to other regions of the Nankai Trough. Drilling results, integrated with observations from seismic ...
The conventional view of plate boundary strain during the seismic cycle in subduction zones portrays the accretionary margin and upper-plate wedge as the primary site of intra-seismic strain accumulation and co-seismic strain release. This textbook model provides a mechanism for tsunamigenesis, and the accumulation of residual deformation over numerous ...
The conventional view of plate boundary strain during the seismic cycle in subduction zones portrays the accretionary margin and upper-plate wedge as the primary site of intra-seismic strain accumulation and co-seismic strain release. This textbook model provides a mechanism for tsunamigenesis and the accumulation of residual deformation over numerous ...
Deep-penetration seismic reflection profile RU-3 crosses the central California margin southwest of Morro Bay and shows the Paleogene subduction zone as well as compressional and extensional features of the overlying accretionary wedge. Lower plate rocks are indicated by deep, gently dipping reflectors that extend beneath the continental margin for at ...
This study analyzes mathematically the orientation of the superior tibial epiphysis in frontal and sagittal planes for knees with genu varum arthrosis. The assessment of the opening is determined mathematically for the osteotomies; this leads to the establishment of tables which can be used in practise during upper tibial osteotomies. PMID:1494701
Investigations of seafloor morphology and sediment deposits associated with the incision of the South Colombia active margin by a major submarine canyon system are used to reveal out-of-sequence fault activity at least since the Middle Pleistocene. The South Colombian convergent margin is located along Northwestern South America, where the Nazca plate underthrusts eastward the South America plate ...
The "Macalube di Aragona" area is located in Central Sicily (Italy) within a thick accretionary wedge (up to 6 km), developing along the frontal part (Southern margin) of the Sicilian thrust belt. Mud volcanoes are among the most important natural emissions of waters, oil and gaseous hydrocarbons from buried sediments. We have ...
The Calabrian Arc (CA) is a subduction system related to the slow convergence between Africa and Eurasia, well comparable in its geodynamic evolution to the adjacent Mediterranean Ridge against which it impinges in the eastern side of the Ionian Sea. The external part of the arc is represented by a well developed accretionary complex resting on the seaward dipping continental ...
Useful geodynamic distinction of continental collision zones can be based on the degree of rheological coupling of colliding plates. Coupled active collision zones (which can be either retreating or advancing) are characterized by a thick crustal wedge and compressive stresses (i.e. Himalaya and Western Alps), while decoupled end-members (which are always retreating) are ...
The Lengguru accretionary wedge (West Papua) is located in a very active geodynamical context. It results from the oblique convergence between the Pacific plate and the Australian plate. All the wedge has been build between 11 and 2 Ma (Bailly et al., 09). Exceptional boulders of fresh eclogites were discovered in the internal part of ...
In the Val Strona di Omegna, Southern Alps, a subvertically tilted accretionary wedge sequence of a Carboniferous accretion-subduction complex overlies an intrusive complex attributed to Late Carboniferous to Permian magmatic underplating events [1]. A detailed mapping of this cross-section through the base of the crust revealed the presence of a swarm of ...
The Lesser Antilles subduction zone has produced no recent strong thrust earthquakes, making it difficult to quantify the seismic hazard from such events. The Lesser Antilles arc has a slow convergence rate (2cm/yr) overall and a very wide accretionary wedge (200-300 km) at its southern end. To investigate the effect of the ...
Several studies describe sagittal realignment for flat back and related kyphotic decompensation. Official guidelines for sagittal and the frontal realignment have not been developed. In this retrospective study, the authors examined 10 patients with flat back syndrome and treated a related kyphotic decompensation syndrome by posterior wedge osteotomy. The ...
During dextral oblique translation along Laurentia in western Idaho, the Blue Mountains superterrane underwent clockwise rotation and impinged into the Syringa embayment at the northern end of the Salmon River suture. Along the suture, the superterrane is juxtaposed directly against western Laurentia, making this central Cordilleran accretionary-margin segment unusually ...
USGS Publications Warehouse
The Falls Lake melange crops out in the eastern Piedmont of North Carolina between the Carolina slate belt and the Raleigh belt. The melange is composed of mafic and ultramafic blocks and pods of diverse shapes and sizes, dispersed without apparent stratigraphic continuity, in a matrix of pelitic schist and biotite-muscovite-plagioclase-quartz gneiss. Textures and structural relationships suggest ...
The Southern Apennines chain is a fold-and-thrust belt resulting from the convergence of the African and European plates and simultaneous roll-back of SE-directed Ionian subduction (Upper Oligocene-Quaternary). Ophiolites in the Southern Apennines are related to northwest subduction of the oceanic lithosphere pertaining to the Ligurian sector of the Jurassic western Tethys. The ophiolitic ...
Thrust belts and foreland areas are characterized by a fluxural depression lying between the subducting lithospheric plate and the topographic surface. This depression is continuously filled with tectonic units (accretionary prism) and synorogenic deposits (foredeep basin). Internal geometry of this wedge evolves continuously through time in response to ...
The review addresses such earth- and planetary-science subjects as the origin and early evolution of life on earth encompassing the origin of the first cells and life in the universe, the nature of the earth's core, applications of synchrotron radiation in the earth science, and studies of a volcanic region. A critical taper model of fold-and-thrust belts and accretionary ...
Along a 10-km length of coast north of the Mendocino triple junction, a Neogene accretionary complex has been uplifted >=2 km and tilted northward in response to the interaction of the southern Juan de Fuca (Gorda) plate with the older North American and Pacific plates. These plate interactions were accompanied by tectonic intercalation of Miocene to Pliocene deposits of ...
We have installed a suite of 18 GPS receiver across the Bengal Basin, covering the country of Bangladesh, near the junction of the Indian Shield, the Himayalan collision belt and the Burma Arc subduction zone. The crust of the Indian Shield thins eastward across the hinge zone of an Early Cretaceous continental margin. The thin continental and/or oceanic crust of the eastern Bengal Basin beyond ...
Fluids play a critical role in subduction zones and arc magmatism. At shallow levels in subduction zones (<40 kilometers depth), expulsion of large volumes of pore waters and CH(4)-H(2)O fluids produced by diagenetic and low-grade metamorphic reactions affect the thermal and rheological evolution of the accretionary prism and provide nutrients for deep-sea biological ...
We describe results of an active-source seismology experiment across the Chilean subduction zone at 38.2�S. The seismic sections clearly show the subducted Nazca plate with varying reflectivity. Below the coast the plate interface occurs at 25 km depth as the sharp lower boundary of a 2-5 km thick, highly reflective region, which we interpret as the subduction channel, that is, a zone of ...
Single-channel and multichannel seismic reflection profiles of the North Scotia ridge trending west-east off southernmost South America show the north side to consist of a wedge of deformed sediments resting on a planar layered sequence. Relative movement of the ridge northward toward the Falkland plateau has resulted in deformation and uplift of the near-surface sediment ...
The Taiwan orogen has long been the focus of theoretical studies on the relationships between surface processes, tectonics and climate. As a result Taiwan has become famous as an example of the steady evolution of orogenic wedges where erosion triggered by seasonal tropical typhoons balances the accretionary influx. One main assumption under these ...
A synthesis of published work and preliminary results from a multidisciplinary study of the various crustal levels exposed in the island of Naxos in the Cyclades allows to propose a model for the evolution of the orogenic accretionary wedge in this region. Naxos is characterized by the juxtaposition of metamorphic rocks and Late Oligocene- Early Miocene to ...
A 200km wide grounding zone system in outer Bj�rn�yrenna (Bear Island Trough), south-western Barents Sea, has been investigated using 2D high resolution seismic, sediment gravity cores, regional SWATH and large scale bathymetry data (Fig. 1). Preliminary results suggest the sediment wedge to originate from oscillations of the Bj�rn�yrenna Ice Stream during the ...
This paper discusses the nature and origin of subsurface sediment mobilization processes in deep marine clay-rich environments. In the studied area of the southern Barbados accretionary prism, new geophysical acquisitions have emphasized the spectacular widespread development of mud volcanoes that are well-developed along ramp anticlines and along sigmoidal rises with trends ...
The composition of pore fluids, particularly the Li^+ and Cl^- distributions, are known to be useful indicators of fluid sources and migration patterns in accretionary margins, and can provide clues to the source and flux of methane to the gas hydrate stability zone (GHSZ). The distribution of dissolved Li+ in pore waters from Leg 204 is characterized by an initial lithium ...
The island of Barbados exposes the crestal zone of the remarkably broad accretionay prism of the Lesser Antilles forearc. The architecture of Barbados is three-tiered: an upper arched cap of Pleistocene reefs that record rapid and differential uplift of the island, an intermediate zone of nappes of mainly abyssal or deep bathyal pelagic rocks, and basal complex whose lithotypes extend to ...
We investigate the internal deformation of orogenic wedges growing by frontal accretion with a two-dimensional numerical model. Our models are limited to crustal deformation and assume a horizontal detachment as observed for various natural orogens (e.g. Alaska and Costa Rica). The model wedges develop as a result of convergence of a ...
PURPOSE: The purpose of this study was to clarify the causes of the increase in the posterior tibial slope during open-wedge high tibial osteotomy (HTO) and to investigate whether its changes influenced the correction angle in frontal plane. METHODS: We retrospectively reviewed 20 patients (26 knees) treated with open-wedge HTO. They ...
IODP Expedition 315 targeted the hangingwall of an out-of-sequence thrust fault that is thought to rupture during great earthquakes, and to be tsunamigenic. More than 300 faults observed in core from sites C0001 and C0002 provide constraints on the direction and sense of slip in the forearc basin fill/slope cover, and in the underlying accretionary prism. Paleomagnetic data ...
Santonian, Campanian, and Maestrichtian deposystems of the Sacramento basin of California consist principally of deltaic slope, deep-sea-fan, and basin-plain lithofacies that generally prograded southward and westward into the basin from magmatic-arc source areas located to the east in the Sierra Nevada and to the north in the Klamath Mountains area. The basin formed in the northern part of the ...
Recent work suggests the following for the tectonic architecture of the central Georgia Eastern Piedmont. The Alleghenian-age, Modoc fault zone (MZ), first defined in S. Carolina, continues along strike (c. S60W) at least to the Ocmulgee R. (net length = 250 km), where it converges with the Ocmulgee (OF) and Goat Rock (GR) faults. Diverging to the S from the MZ is a sharp contact between ...
Most of China and Soviet Asia were formed by the welding of microcontinents and accretionary wedge assemblages from the Devonian through the Late Cretaceous. The first hydrocarbon systems developed in late Precambrian to middle Paleozoic basins on continental platform blocks prior to the Hercynian welding of plates. Later hydrocarbon systems developed in ...
The easternmost part of the Nankai accretionary complex (Tokai area) is presently underthrust by a large basement ridge going into subduction and known as the Paleo-Zenisu ridge. As a consequence, the upper margin has recorded a large finite compressional deformation with broad folding of the forearc basin as well as localized active faults known as Enshu fault, Kodaiba fault ...
The Nias forearc basin is a 250-km long, 100-km wide bathyal depression located between the mainland of west-central Sumatra and the island of Nias. A grid of multichannel reflection seismic data covering the basin and adjacent shelves was used to map Neogene structure and to delineate the Neogene seismic stratigraphy. Six major structural features, including the continental margin, strike-slip ...
Eugeoclinal terranes represented in the Koeli Nappes were thrust > 500 km onto the Baltoscandian platform during the early to middle Paleozoic. Underlying thrust sheets of the Seve Nappe complex are suspected to have been derived from the outer margin of continent Baltica. Contrasting tectonothermal histories are recorded in Seve and Koeli Nappes. Eclogite-bearing Seve rocks underwent an ...
The Sava Zone of the northern Dinarides in Former Yugoslavia is part of the Cenozoic Adria-Europe plate boundary. Late Cretaceous subduction of remnants of Meliata-Vardar oceanic lithosphere led to the formation of a suture, across which upper-plate European units were juxtaposed with Adria-derived units of the Dinarides. Late Cretaceous siliciclastic sediments were incorporated into an ...
The Sava Zone of the northern Dinarides is part of the Cenozoic Adria-Europe plate boundary. Here Late Cretaceous subduction of remnants of Meliata-Vardar oceanic lithosphere led to the formation of a suture, across which upper plate European-derived units of Tisza-Dacia were juxtaposed with Adria-derived units of the Dinarides. Late Cretaceous siliciclastic sediments, deposited on the Adriatic ...
The Gibraltar arc encompasses the Betic - Rif mountain belts with outward directed thrusting, surrounding a zone of strong Neogene subsidence and crustal thinning in the Western Alboran Sea. The SISMAR marine seismic survey conducted in April 2001 acquired over 3000 km of 360-channel seismic data with a 4.5 km long streamer and 1000 km of wide-angle data recorded by ocean bottom seismometers ...
The great February 27, 2010 Mw 8.8 earthquake off the coast of southern Chile ruptured a 606 km length of subduction zone. In this study we make two independent estimates of shear stress in the crust in the region of the Chile earthquake. First, we use a coseismic slip model constrained by geodetic observations from InSAR and GPS to derive a spatially variable estimate of the change in static ...
The authors have imaged nearly the entire North Panama thrust belt (NPTB) to determine the dynamics of the Panama arc colliding end-on with South America. Observations support a simple flexural beam model in which eastward collision of the arc against the continent is transformed into northward relative motion of the NPTB. Fold axes and thrust faults within the NPTB show remarkable uniformity in ...
The Gibraltar region features the arcuate Betic - Rif mountain belt with outward di- rected thrusting, surrounding a zone of strong Neogene subsidence and crustal thin- ning in the Western Alboran Sea. Until now its geodynamic interpretation has re- mained controversial. The Gibraltar Arc is located at the eastern end of the Azores- Gibraltar transform, a diffuse transpressional plate boundary ...
The Coulomb critical taper model has been very successful in explaining the large-scale topography of a number of terrestrial accretionary wedges; however, this model is limited to cases of purely brittle-frictional deformation. In this paper we extend te range of applicability of the critical taper model by explicity including the effects of ...
The Coulomb critical taper model has been very successful in explaining the large-scale topography of a number of terrestrial accretionary wedges; however, this model is limited to cases of purely brittle frictional deformation. In this paper the authors extend the range of applicability of the critical taper model by explicitly including the effects of ...
Stabilization Wedges are "wedges" that need to be cut out of predicted carbon emissions to avoid doubling ... ...
... wedge. A highly stratified wedge is common to deep rivers with high freshwater flows such as the Mississippi. ... ...
New field investigations in the area between Sidi Allal Tazi, Moulay Bouselham and Larache (North Western Coastal Morocco) revealed the existence of important neotectonic features. Field research was undertaken in order: (1) to look for an eventual continuation onshore of the southern front of the accretionary wedge of the Gulf of Cadiz and (2) to choose ...
In 2009 we conducted a seismic experiment with the R/V Marcus G. Langseth in conjunction with the TAIGER project in the deep water Luzon Strait offshore Taiwan. The program acquired 12 high-quality MCS and OBS profiles across the Manila subduction zone in an effort to gain a further understanding of the crustal evolution of pure subduction south of ~20.5� N to initial-stage arc-continent ...
Along the eastern border of the Caribbean plate the Lesser Antilles islands form an active volcanic arc above the Atlantic subducting lithosphere. The crustal structure of this convergent margin is presented here from first arrival tomographic inversion of a 3D wide-angle seismic dataset acquired offshore Dominica and Martinique islands by a network of 27 Ocean Bottom Seismometers (OBS). The ...
To understand the evolution of mechanical and hydraulic properties of sediments during burial, underthrusting, underplating, accretion, and exhumation within accertionary subduction zones, triaxial deformation experiments were conducted on consolidated sediment from the Nankai Trough sampled during the Integrated Ocean Drilling Program (IODP) Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) ...
During conventional reconstruction of the auricle in patients with microtia, simply separating the auricle from the mastoid region with a full-thickness skin graft usually fails to create firm elevation and sufficient projection. To achieve frontal symmetry is difficult, and sometimes the normal auricle needs to be set back. We reconstructed the auricle in patients with ...
The existence of thin intact thrust sheets as long as 200 km implies very weak detachments relative to their internal strength, which is the classic thrust-fault problem addressed by Hubbert & Rubey (1959). Low-taper critical-taper wedges also require weak detachments relative to wedge strength (Davis et al. 1983). The causes and absolute magnitudes ...
During Ocean Drilling Program (ODP) Leg 196, Logging-While-Drilling (LWD) data were collected at two sites spanning the deformation front of the Nankai Trough accretionary prism. Site 1173 penetrated ~750 m of sediment of the Shikoku Basin, about 10 km seaward of the prism, and Site 808 penetrated to the basal decollement several km landward of initial thrust formation. ...
Accretionary complexes host a variety of fault zones that accommodate plate convergence and internal prism deformation, including the d�collement, imbricate thrusts, and out-of-sequence thrusts or splays. These faults, especially the d�collement and major splay faults, are considered to be candidates for hosting slow slip events and large magnitude earthquakes, but it is ...
The Aceh segment of the Sunda Arc absorbed the largest slip along the 26 December 2004 Mw9.2 subduction earthquake rupture and caused the highest and most disastrous tsunami run-ups. Sea floor disruption marks the frontal active part of the accretionary prism along that segment. An ROV, bathymetric, and seismic survey (R/V Natsushima, JAMSTEC 2-3/2005) ...
Analysis of stable isotopes and fluid inclusions in centimeter-scale fibrous quartz-calcite strain fringes from the Taconic thrust belt in Vermont and New York allows reconstruction of fluid conditions and sources over the course of strain-fringe growth. Oxygen isotope ratios in quartz show regular variations in ?18O, ranging between 19.2� and 20.0� in different parts of strain fringes. Fluid ...
Eclogite lenses in the Agualada Unit (western Ordenes Complex, Spain) contain the peak mineral assemblage garnet (prograde rim: Alm = 48 mol%, Prp = 30 mol%), omphacite (Jd max = 36 mol%), quartz, rutile and rare zoisite, which equilibrated at T = 700 �C and P > 12 14 kbar. Garnet shows discontinuous growth zoning, with a pyrope-poor intermediate zone (Alm = 51 mol%, Prp = 10 mol%) between a ...
Fracture porosity in the d�collement zone of Nankai accretionary wedge is estimated by comparison of porosity measured on cores during Ocean Drilling Program Leg 131 and porosity calculated from resistivity logs acquired during Leg 196 using Logging While Drilling. Resistivity is converted to formation factor considering both pore fluid conductivity and ...
Surface waves at short periods (<35s) are affected severely by heterogeneities in the crust and the uppermost mantle. When the scale of heterogeneity is sufficiently large, its effect can be studied in a deterministic way using conventional concepts of reflection and refraction. A well-known example is surface wave refraction at continental margin. We present a case study to investigate the ...
Porous sediments within the frontal portions of active accretionary prisms are subject to concurrent consolidation and diagenesis during burial. The competing effects of these two processes determine the in-situ porosity and effective strength of the sediments that govern the internal structure and deformation behavior of the prism, and ultimately, the ...
Regional variations in sediment thickness, internal structures, average elevation, and Bouguer gravity define a four-component foreland basin system adjacent to the Central Andes. In the most proximal part of the foreland basin system, the eastern Subandean zone and westernmost Chaco Plain, 1 3 km of Cenozoic deposits overlies active folds and thrusts of the frontal Andean ...
Layer-parallel slip is dominant in a wedge tapering about 2{degrees} across the 70-km-wide Kohat foreland fold and thrust belt between the Main Boundary thrust and the Surghar Range of northern Pakistan. Balanced cross sections show over 50% line length shortening by blind or partially emergent folding and thrusting, of which only about half is documented cover sequence ...
Coupled chemical and isotopic signatures in arc lavas are critical for resolving temporal variations in the magnitude, source, and composition of subduction inputs to the slab-mantle interface. Dewatering of the subducting plate within this zone can potentially affect tectonic and igneous processes. In 2006, the National Gas Hydrate program of India drilled a ~700 meter long (~9.4 Ma) marine ...
Using SeaBeam bathymetry and multichannel seismic reflection records we have identified three large submarine landslides on the southern Oregon Cascadia margin. The area enclosed by the three arcuate slide scarps is approximately 8000 km2, and involves an estimated 12,000-16,000 km3 of the accretionary wedge. The three arcuate slump escarpments are nearly ...
Analysis of a 3D seismic volume across the Nankai Trough off Kii Peninsula defines a population of normal faults that indicate subhorizontal extension within the recent (0-3.8 Ma) forearc basin strata. IODP drilling (as part of the Nankai Trough Seismogenic Zone Experiment, or NanTroSEIZE) within the seismic survey area documented an abrupt change in the orientation of the maximum horizontal ...
