ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Publication Date: 2017-06-15
    Description: Logs collected while drilling measured density in situ, through the accretionary prism and decollement zone of the northern Barbados Ridge. Consolidation tests relate void ratio (derived from density) to effective stress and predict a fluid pressure profile, assuming that the upper 100 m of the prism is at a hydrostatic pressure gradient. The calculated fluid pressure curve rises to 〉90% of lithostatic below thrusts in the prism, presumably due to the increase in overburden and lateral tectonic loading. Thin (0.5–2.0 m) intervals of anomalously low density and resistivity in the logs through the basal decollement zone suggest dilation and perhaps hydrofracturing. A peak in hydraulic head in the upper half of the decollement zone requires lateral influx of fluid, a conclusion consistent with previous geochemical studies. Although the calculated fluid-pressure profile is model dependent, its inherent character ties to major structural features.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    Publication Date: 2016-04-26
    Description: Anomalous reflections in marine seismic reflection data from continental slopes are often correlated with the base of gas hydrated sedimentary rocks. Examination of University of Texas Marine Science Institute reflection data reveals the possible presence of such gas hydrates along the east coast of the United States, the western Gulf of Mexico, the coasts of northern Colombia and northern Panama, and along the Pacific side of Central America in areas extending from Panama to near Acapulco, Mexico. Suspected hydrates are present in water depths of 700 to 4,400 m and extend from 100 to 1,100 m subbottom. Geometric relations, reflection coefficients, reflection polarity, and pressure-temperature relations all support the identification of the anomalous reflections as the base of gas hydrated sediments. In most places, gas hydrate association is related to structural anomalies (anticlines, dipping strata), which may allow gas to concentrate and migrate updip into pressure and temperature conditions suitable for hydrate formation. The gas hydrate boundary can be used to estimate thermal gradients. In general, thermal gradients estimated from the gas hydrate phase boundary are higher than reported thermal gradients measured by conventional means.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    Publication Date: 2017-05-17
    Description: Logs collected while drilling measured density in situ, through the accretionary prism and decollement zone of the northern Barbados Ridge. Consolidation tests relate void ratio (derived from density) to effective stress and predict a fluid pressure profile, assuming that the upper 100 m of the prism is at a hydrostatic pressure gradient. The calculated fluid pressure curve rises to 〉90% of lithostatic below thrusts in the prism, presumably due to the increase in overburden and lateral tectonic loading. Thin (0.5–2.0 m) intervals of anomalously low density and resistivity in the logs through the basal decollement zone suggest dilation and perhaps hydrofracturing. A peak in hydraulic head in the upper half of the decollement zone requires lateral influx of fluid, a conclusion consistent with previous geochemical studies. Although the calculated fluid-pressure profile is model dependent, its inherent character ties to major structural features.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Publication Date: 2017-04-10
    Description: The interrelation between deformation styles and behavior of fluids in accretionary prisms is under debate, particularly the possibility that overpressuring within the basal decollement may enable mechanical decoupling of the prism from the subducting material. Anisotropy of magnetic susceptibility (AMS) data from sediments spanning the basal decollement of the Barbados accretionary prism show a striking progression across this structure that strongly supports the hypothesis that it is markedly overpressured. In the accretionary prism, above the decollement, the minimum AMS axes are subhorizontal and oriented nearly east-west, whereas the maximum AMS axes are oriented nearly north-south and shallowly inclined. At the top of the decollement, the minimum AMS axes orientations abruptly change to nearly vertical; this orientation is maintained throughout the decollement and in the underthrust sediments below. The AMS orientations in the prism sediments above the decollement are consistent with lateral shortening due to regional tectonic stress, as the minimum axes generally parallel the convergence vector of the subducting South American plate and the maximum axes are trench-parallel. Because the orientations of the AMS axes in deformed sediments usually parallel the orientations of the principal strains, the AMS results indicate that the incremental strain state in the Barbados prism is one dominated by subhorizontal shortening. In contrast, the AMS axes within and below the decollement are consistent with a strain state dominated by vertical shortening (compaction). This abrupt change in AMS orientations at the top of the decollement at Site 948 is a direct manifestation of mechanical decoupling of the off-scraped prism sediments from the underthrust sediments. The decoupling horizon occurs at the top of the decollement zone, coinciding with the location of flowing, high-pressure fluids.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    facet.materialart.
    Unknown
    In:  Zentralblatt für Geologie und Paläontologie : Teil 1, Allgemeine, angewandte, regionale und historische Geologie
    Publication Date: 2016-04-19
    Keywords: ddc:550
    Type: http://purl.org/escidoc/metadata/ves/publication-types/article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    facet.materialart.
    Unknown
    In:  Zentralblatt für Geologie und Paläontologie : Teil 1, Allgemeine, angewandte, regionale und historische Geologie
    Publication Date: 2016-04-19
    Type: http://purl.org/escidoc/metadata/ves/publication-types/article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    Publication Date: 2013-10-22
    Type: http://purl.org/eprint/type/ConferencePaper
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    facet.materialart.
    Unknown
    In:  Zentralblatt für Geologie und Paläontologie : Teil 1, Allgemeine, angewandte, regionale und historische Geologie ; Year: 1997 ; Issue: 3-6 ; Pages: 393-408
    Publication Date: 2014-08-06
    Description: Combined on- and offshore wide-angle seismic data were collected in southern Costa Rica along a profile that extends from the Middle America Trench and crosses the Pacific continental margin, the isthmus, and reaches to the Caribbean coast. Closely spaced marine airgun sources were used in the Pacific, coincident with the preexisting seismic reflection line P-1600 recorded by SHELL Int. Four large explosive charges were detonated in boreholdes onshore. The combined interpretation of the near-vertical and wide-angle data provides a detailed crustal model. The profile is located on the northern flank of Cocos Ridge, where we have determined that the subducting oceanic plate has a thickness of 11 to 12 km. It dips down with an average angle of 17° and can be imaged to a depth of at least 35 km with the available data. Erosion of the margin wedge is suggested by a thick low velocity zone overlying the downgoing slab. Like elsewhere along the Middle America Trench, the body of rock underlying forearc and slope sediment has high velocities (〉4.0 km/s). At deeper levels (〉5 km), the crustal rocks along the profile generally show high velocities (6.0 to 6.6 km/s). To the southwest, these high velocities can be followed to the mid-shelf area. The inverted Térraba Basin contains intermediate velocity sediment (3.0 km/s) with a total thickness of about 2 km. The Limón Basin has up to 6 km of Tertiary and Quaternary sediment. An intracrustal discontinuity is found at a depth of about 18 km, but cannot be determined in detail due to the limited offset of the available data.
    Type: http://purl.org/escidoc/metadata/ves/publication-types/article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    Publication Date: 1988-02-01
    Description: Краткое содержаниеС помощью сейсмическ их методов исследова ния в трех регионах средне й Америки удается под робнее исследовать породы в доль плоскости срыва, которая отделяет засасываем ые и «перемещенные» с едименты. По этим данным, получе нным вдоль названной системы засасывания, можно представить се бе механизм образовани я срывов и влияние мес тных факторов на условия и х образования. Незави симо от того, повлияла-ли, или н ет топография поверх ности ландшафта погружающ егося основания на ср ыв, место возникновения последнего зависит о т типа и мощи седиментов граб ена. Там, где погружающ ийся фундамент и полупела гические седименты о кеанической плиты перегружены пе счаниками, и терриген ными турбидитами, как напр.: отрезок грабена в Мексике, срыв проходи т вблизи основания ту рбедитного профиля. Погружающие ся нарушенные глыбы океанической к оры контролируют обр азование рампы надвигов, приче м выше рамп появляютс я антиклинали. Там, где п листые турбидиты гра бенов покрывают засасывае мый топографический ландшафт (напр.: Гватемала), скол проходит примерно 100 м под поверхностью се диментов и подлежащи й погружающийся топог рафический ландшафт (Гватемала) не оказывает влияния на линию отслаивания. Засасываются нижние 200–300 м седимента грабен а и все пелагические от ложения. Там, где богат ые карбонатами седимен ты океанической плит ы не перекрыты седимента ми грабена, напр.: Коста-Рика, отслаивание проходи т в осадочном столбе погружающейся плиты. Отслаивание см ещается в одном и том же стратиграфич еском горизонте и ско льзит при этом по и над погру жающейся глыбе горст а.Seismic reflection data from three areas of the Middle America Trench provide insights into the behavior of the decollement that separates subducted and offscraped sediment. The range of responses observed along this single subduction system provides clues as to how the decollement forms and is influenced by local conditions. The location of the decollement and whether or not the subducting basement topography influences the decollement are apparently controlled by the type and thickness of sediment in the trench. Where subducting basement topography and oceanic plate hemipelagic sediments are buried by sandy terrigenous turbidites, such as in the trench axis off Mexico, the decollement is localized near the base of the turbidite section. Subducting normal fault blocks in the oceanic crust control thrust ramps, and hanging wall anticlines form above the ramps. In regions of the trench where coarse terrigenous sediment is thin or absent, the decollement is localized within the incoming sediment section. Where muddy trench turbidites bury subducting topography (e.g. off Guatemala), the decollement is approximately 100 m deep and is little affected by the underlying subducting topography. The lower 200–300 meters of trench sediment and all of the pelagic sediment are subducted. Where there is no trench sediment overlying carbonate-rich oceanic plate sediments (e.g. off Costa Rica), the decollement is located within the subducting plate sediment section. The decollement is localized at a single stratigraphic level and rides up and over subducting horst blocks.ZusammenfassungReflektionsseismische Daten aus drei Bereichen des Mittel-Amerika-Grabens geben Einblick in das Verhalten entlang einer Abscherung in der subduziertes und »abgeschabtes« Sediment voneinander getrennt werden. Die Daten, die entlang dieses Subduktionssystems erhalten wurden, liefern Anhaltspunkte darüber, wie sich die Abscherung bildet und wie sie von lokalen Bedingungen beeinflußt wird. Der Entstehungsort der Abscherung wird, unabhängig davon, ob die abtauchende Basementtopographie die Abscherung beeinflußt oder nicht, anscheinend von Typ und Dicke der Grabensedimente kontrolliert. Dort, wo das abtauchende Basement und die hemipelagischen Sedimente der ozeanischen Platte von sandigen, terrigenen Turbiditen überlagert werden, wie im Grabenabschnitt vor Mexico, liegt die Abscherung nahe der Basis des Turbiditprofiles. Abtauchende, normal gestörte Schollenblöcke der ozeanischen Kruste kontrollieren die Bildung von Überschiebungsrampen unter Bildung von Antiklinalen oberhalb dieser Rampen. Wo schlammige Grabenturbidite die subduzierende Topographie überdecken (z.B. vor Guatemala), liegt die Abscherung etwa 100 m unter der Sedimentoberfläche und wird kaum von der unterlagernden, abtauchenden Topographie beeinflußt. Die unteren 200–300 m der Grabensedimente sowie die gesamten pelagischen Ablagerungen werden subduziert. Wo karbonatreiche Sedimente der ozeanischen Platte nicht von Grabensedimenten überlagert werden (z.B. vor Costa Rica) liegt die Abscherung innerhalb der Sedimentsäule der abtauchenden Platte. Die Abscherung bewegt sich in einem einzigen stratigraphischen Niveau und gleitet dabei auf und über abtauchende Horstschollen.RésuméDes prospections par sismique-réflexion, effectuées dans trois régions de la fosse d'Amérique Centrale, éclairent le comportement du décollement qui sépare les sédiments subductés des sédiments «raclés». Les donnés recueillies le long de ce système de subduction simple fournissent des indications sur la manière dont le décollement prend naissance et est influencé par les conditions locales. L'emplacement du décollement et le fait qu'il est, ou non, influencé par la topographie du substrat en subduction dépendent, semble-t-il, de la nature et de l'épaisseur des sédiments de la fosse. Lorsque, dans la plaque océanique en subduction, la topographie du socle et les sédiments hémipélagiques surincombants sont enfouis sous des turbidites terrigènes arénacées, comme c'est le cas au large du Mexique, le décollement se produit près de la base de la série turbiditique. La subduction de blocs découpés par des failles normales dans la croûte océanique détermine des rampes de charriage au-dessus desquelles prennent naissance des structures anticlinales. Dans les parties de la fosse qui sont pauvres en sédiments terrigènes grossiers ou qui en sont dépourvues, le décollement est situé à l'intérieur de la série sédimentaire. Lorsque le relief de la plaque en subduction est enfoui sous des turbidites boueuses (p. ex. au large du Guatemala), le décollement se situe à 100 m sous la surface supérieure des sédiments et est peu affecté par la topographie du substrat subducté. La subduction affecte alors la partie inférieure (200 à 300 m) des sédiments de la fosse, ainsi que l'entièreté des sédiments pélagiques. Lorsqu'il n'y a pas de sédiments terrigènes recouvrant les dépôts carbonates de la plaque océanique (p. ex. au large de Costa Rica), le décollement se situe au sein de ces derniers; il correspond à un niveau stratigraphique et contourne par en-haut les blocs en horst de la plaque descendante. ©1988 Ferdinand Enke Verlag Stuttgart
    Print ISSN: 1437-3254
    Electronic ISSN: 1437-3262
    Topics: Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...