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Plattenkinematische Rekonstruktionen mit herkömmlichen Methoden können zu großen Fehlern führen, wenn sie in Regionen angewandt werden, in denen Spreizungsanomalien und Fracture Zones fehlen. Die Folgen solcher Fehler sind Überlappungen von Platten, weil deren Ausdehnung in früheren Zeiten geringer ist als die Annahme starrer Plattengrenzen vorhersagt. Dies ist insbesondere der Fall in gedehnter kontinentaler Kruste, weil hier die Information, die in ozeanischer Kruste gespeichert sind, fehlen. Dort ist die Krustenmächtigkeit oft das einzige Indiz zur Rekonstruktion. Liegen flächenhafte Krustenmächtigkeitsdaten vor, so können damit die Lage der Platten rekonstruiert werden.Wir stellen eine neue Rekonstruktionsmethode vor, die eine Krustenmächtigkeitskarte aufteilt in verschiedene Platten, indem Extension durch tiefe Störungen simuliert wird. Dadurch können Teile des Krustenmächtigkeitsgrids wie in einer herkömmlichen Rekonstruktionsmethode rotiert und gegeneinander verschoben werden. Wird eine Verteilung der Krustenmächtigkeiten vor der Extension angenommen werden (z.B. gleichmäßige Mächtigkeiten), kann dies die Qualität einer Rotation anzeigen und verschiedene Rotationen können miteinander verglichen werden, so daß der beste Rotationspol ermittelt werden kann. Wir zeigen den Erfolg dieser Methode am Beispiel Neuseelands, das von etlichen Gebieten gedehnter kontinentaler Kruste, wie z.B. dem Great South Basin, umgeben ist.

The Amundsen Sea Embayment of West Antarctica is in a prominent location for a series of tectonic and magmatic events from Paleozoic to Cenozoic times. It played a central role in the rifting and break-up of greater New Zealand from West Antarctica as it is the location where the junction of Chatham Rise and Campbell Plateau (New Zealand) lies conjugate to the West Antarctic margin. New seismic, magnetic and gravity data from the Amundsen Sea Embayment and Pine Island Bay reveal the crustal thickness and tectonic lineations. The Moho is 24-22 km deep on the shelf. NE-SW trending magnetic and gravity anomalies and the thin crust indicate a former rift zone that was active during or in the run-up to breakup between Chatham Rise and West Antarctica before or at 90 Ma. NW-SE trending gravity and magnetic anomalies, following a prolongation of Peacock Sound between Thurston Island and Ellsworth Land, indicate the extensional southern boundary to the Bellingshausen Plate which was active between 79 and 61 Ma. However, both lineation trends, NE-SW and NW-SE, seem to be observed over broad regions. This infers stepwise and multiple rift and extension phases over a wide period of time before, during and after the break-up between New Zealand and West Antarctica.

The Amundsen Sea embayment of West Antarctica is in a prominent location for a series of tectonic and magmatic events from Paleozoic to Cenozoic times. Seismic, magnetic and gravity data from the embayment and Pine Island Bay (PIB) reveal the crustal thickness and some tectonic features. The Moho is 24-22 km deep on the shelf. NE-SW trending magnetic and gravity anomalies and the thin crust indicate a former rift zone that was active during or in the run-up to breakup between Chatham Rise and West Antarctica before or at 90 Ma. NW-SE trending gravity and magnetic anomalies, following a prolongation of Peacock Sound, indicate the extensional southern boundary to the Bellingshausen Plate which was active between 79 and 61 Ma.

Die Prozesse, die zum intrakontinentalen Rifting und nachfolgenden Abbruch führen und ihn begleiten, sind weiterhin nur teilweise verstanden. Neueste plattentektonische Rekonstruktionen des Südpazifiks zeigen, daß der kretazische Abbruchprozeß von Neuseeland und der Westantarktis in sehr unterschiedlichen Phasen und Zeiten abgelaufen ist. Ein erstes Rifting zwischen dem Chatham Rise und dem östlichen Marie-Byrd-Land bzw. dem westlichen Thurston-Island-Block der Antarktis fand um 90 Ma statt (Abb. 1), nachdem vermutlich die Kollision des Hikurangi-Plateaus mit dem ehemaligen Chatham Rise den proto-pazifischen Subduktionsvorgang entlang des damaligen Nordrands von Neusee-land beendete. Das benachbarte Campbell-plateau trennte sich von Marie-Byrd-Land erst um 83 Ma. Der dazwi-schenliegende Zeitraum ist durch enorme Extensionsprozesse der neuseeländischen Kruste gekennzeichnet, die den Bountytrog und das Great South Basin als breite und tiefe Sedi-mentbecken formieren ließen.Als Teil des Projekts CAMP wird mit den während der Fahrt SO-169 (Jan./Feb. 2003, Abb. 2) gewonnenen geophysikalischen Daten der Fragestellung nachgegangen, welche Rolle die Öffnung des Bountytrogs und des Great South Basins sowie das Campbellplateau für den kontinentalen Abbruchprozeß spielten. Über beide Becken und Abschnitte des Plateaus sind sowohl reflexionsseismische als auch Weitwinkelreflexions- und Refraktionsprofile mit Ozeanbodenseismometern (OBS) vermessen worden. Die OBSe sind im Abstand von jeweils ca. 15 km zueinander entlang zweier Profile abgesetzt worden und haben Airgun-Signale im nominellen Schußabstand von 150 m registriert. Landwärts wurde das Great-South-Basin-Profil mit weiteren seismischen Registriereinheiten verlängert. Begleitet wurden alle Schiffsprofile mit Gravimetrie- und Magnetfeldmessungen. Die Auswertung der neu gewonnenen Daten wurde von weiteren, älteren reflexions-seismischen Daten, die von GNS Science zur Verfügung gestellt wurden. Infolge der Auswertung wurden

Remarkably little is known about the Cretaceous rifting process between New Zealand and Antarctica as well as within the submarine parts of the microcontinent of New Zealand itself. The Bounty Trough offers good insights into these break-up processes. Here we present results from a combined gravity, multichannel seismic and wide-angle reflection/refraction seismic transect across the Bounty Trough and interpret this on the basis of velocity distribution and crustal composition derived from Poisson's ratio and P-wave velocity. The lower crust exhibits a high-velocity (vp "ca." 7 - 7.7 km/s, vs "ca." 3.9 - 4.5 km/s), high-density body ("rho" "equals" 3.02 kg/cm³) at the location of the most thinned crust of the Bounty Trough. In this part, crustal thickness is reduced from 22 - 24 km beneath Chatham Rise and Campbell Plateau to about 9 km. We interpret this high-velocity/density body as a magmatic intrusion into a thinned continental crust. Our results show that the Cretaceous rifting of the Bounty Trough is very likely not the result of back-arc extension caused by the Hikurangi Plateau subduction in the Gondwana margin, but of continental break-up processes related to the separation of New Zealand from Antarctica. Rifting ceased at the onset of seafloor spreading, so that only little oceanic crust was produced in the Middle Bounty Trough. Comparisons with the Oslo Rift and the Ethiopian/Kenya Rift indicate analogue systems and imply a stretching model that combines uniform stretching and simple shear extension.

The Campbell Plateau and Chatham Rise are large submarine plateaux of continental origin forming parts of the submarine New Zealand continent. Prior to the break-up of this part of Gondwana, New Zealand was situated at the proto-Pacific plate boundary of Gondwana, connected to Marie Byrd Land. It is expected that the development of the continental fragments forming Campbell Plateau and Chatham Rise played a key role in the development of Gondwanas plate boundary from a convergent margin to continental rifting. Our new crustal models of Bounty Trough and Great South Basin infer thinned crust beneath both basins. The crust beneath the Bounty Trough is extremely thinned up to nascent seafloor spreading. Seismic information implies that several extensional phases and styles (pure shear and simple shear) have occurred. Beneath the Great South Basin, the crust is less thinned and underplating can be observed in some areas. Our models as well as geologic information suggest, that an initial extension of the Campbell Plateau predates the Great South Basin opening in Cretaceous time. This information related to the magnitude and style of rifting along Bounty Trough and Great South Basin, influence models of the break-up process between New Zealand and Antarctica that will be presented here.

Accurate models of the geodynamic-tectonic evolution contain some of the most important parameters for understanding and reconstruction of the respective regional and global palaeo-environment. The region of the Amundsen Sea embayment and Pine Island Bay is of great importance for understanding both tectonic and sedimentary processes of West Antarctica. Tectonically, the Amundsen Sea embayment lies between the Palaeozoic crustal blocks of Marie Byrd Land, Ellsworth Land and Thurston Island. Its continental margin is conjugate to the passive margin of the eastern New Zealand submarine continental plateaux and Bounty Trough which underwent major extension during Cretaceous rifting between New Zealand and West Antarctica. Later, the embayment seemed to have played a role as a plate boundary when the Bellingshausen Plate acted independently as a microplate until the early Tertiary. It can be assumed that the tectonic architecture with the formation of deep basins and erosional troughs laid the foundation for major glacier outflow of the West Antarctic Ice-Sheet (WAIS) into Pine Island Bay and the South Pacific since early West Antarctic glaciation.During RV Polarstern expedition ANT-XXIII/4 (Feb-Apr 2006), and in cooperation with the RMS James Clark Ross cruise JR141 (Jan-Feb 2006), we intend to collect seismic, bathymetric, sub-bottom profiles as well as helicopter-magnetic data from the inner shelf, outer shelf, slope and deep sea of the Amundsen Sea embayment and Pine Island Bay to address tectonic as well as sedimentary objectives. We will present first results of both expeditions.

Rift systems give important insights into the processes that control the beginning extension and subsequent break-up of continents. Quantifying the amount of crustal stretching and the position of the continent-ocean boundary helps refining plate-kinematic reconstructions, as this will overcome problems in previous models which were based on rigid plate assumptions. The submarine continental plateaux off southeastern New Zealand (NZ), Chatham Rise (CR) and Campbell Plateau (CP), were adjacent to Marie Byrd Land (MBL) of Antarctica until extension and subsequent seafloor spreading formed the Southern Ocean in the Late Cretaceous. While the timing of the BT opening between CR and CP is indirectly derived from plate-tectonic evidence, the processes of extension of the Bounty Trough (BT) and the development of the fragments forming CR and CP are not yet understood. Models suggest either a rift system of the Southern Pacifics early opening or a subsequent opening of an already existing back-arc basin, a proto-BT.To investigate the evolutionary processes of these submarine plateaux, a geophysical and geological survey was conducted across CP and BT in early 2003 with the German R/V SONNE during cruise SO-169 (project CAMP). The survey carried out two deep crustal seismic transects and a series of multichannel seismic reflection lines across GSB and across BT.Velocity-depth and gravity models infer an extremely thinned crust beneath the Bounty Trough and the Great South Basin (GSB). The thickness of the crystalline crust is reduced from 20-23 km under the CR and the CP to some 12 km under the BT. Beneath the GSB, the crystalline crust thins to some 14 km from about 26 km towards CP and the South Island of NZ. P- and S-velocities are significantly increased directly beneath the Bounty Channel. We interpret a high-velocity, high-density body in the BT as a magmatic intrusion into thinned continental crust. Crustal thinning ceased shortly prior to the onset of seafloor spread

Multichannel seismic (MCS) data from the Yaquina forearc basin off Peru reveal a complex distribution of gas and gas hydrate related reflections. Lateral variations of the reflection pattern at the assumed base of the gas hydrate stability zone in terms of continuity, amplitude, and signal attenuation underneath are observed, as well as the possible occurrence of paleo-bottom simulating reflectors (BSRs). Phase reversed reflections above the bottom simulating reflector point to free gas within the gas hydrate stability zone (GHSZ). To constrain the interpretation of the observed reflection pattern we calculated the velocity distribution along the MCS line from high-resolution ocean bottom hydrophone recordings with two independent methods. Heat flux values estimated on the basis of the velocity-depth functions increase with decreasing amplitude of the BSR and peak near chemoherms. These results suggest a model of the Yaquina Basin where free gas is trapped under parts of the BSR, and within the GHSZ, particularly under the seafloor and under an erosional unconformity. The hypothesis of a paleo-BSR that reflects the uplift of the base of the hydrate stability zone caused by the deposition of a particular sediment sequence is supported by the estimated heat flux values.

Die Prozesse, die zum intrakontinentalen Rifting und nachfolgenden Abbruch führen und ihn begleiten, sind weiterhin nur teilweise verstanden. Neueste plattentektonische Rekonstruktionen des Südpazifiks zeigen, dass der kretazische Abbruchprozess von Neuseeland und der Westantarktis in sehr unterschiedlichen Phasen und Zeiten abgelaufen ist. Ein erstes Rifting zwischen dem Chatham Rise und dem östlichen Marie Byrd Land bzw. dem westlichen Thurston-Island-Block der Antarktis fand um 90 Ma statt (Abb. 1), nachdem vermutlich die Kollision des Hikurangi Plateaus mit dem kontinentalen Chatham Rise den proto-pazifischen Subduktionsvorgang entlang des damaligen Nordrands von Neuseeland beendete. Das benachbarte Campbell Plateau trennte sich von Marie Byrd Land erst um 83 Ma. Der dazwischen liegende Zeitraum ist durch enorme Extensionsprozesse der neuseeländischen Kruste gekennzeichnet, welche den Bounty Trog (zwischen Campbell Plateau und Chatham Rise) und das Great South Basin (Campbell Plateau) als breite und tief ausgelegte Sedimentbecken formieren ließen.Als Teil des Projekts CAMP wird mit den während der Sonne-Fahrt SO-169 (Jan./Feb. 2003) gewonnenen geophysikalischen Daten der Fragestellung nachgegangen, welche Rolle der Bounty Trog und das Great South Basin sowie das Campbell Plateau für den kontinentalen Abbruchprozess spielten. Über beide Becken und Abschnitte des Plateaus sind sowohl reflexionsseismische als auch Weitwinkelreflexions- und Refraktionsprofile mit Ozeanboden-seismographen (OBS) vermessen worden (Abb. 2). Die OBS-Systeme sind im Abstand von jeweils ca. 15 km zueinander entlang zweier Profile abgesetzt worden und haben Airgun-Signale im nominellen Schussabstand von 150 m registriert.Landwärts wurde das Great-South-Basin-Profil mit weiteren seismischen Registriereinheiten verlängert. Begleitet wurden alle Schiffsprofile mit Gravimetrie- und Magnetfeld-Registrierungen. Die Auswertung der neu gewonnenen Daten wird unterstützt von weiteren, meist älteren r

Der östliche Kontinentalrand Neuseelands wird durch den Bounty Trog unterbrochen, ein in der Kreide abgestorbenes Riftsystem. Die während der Sonne-Reise SO-169 gewonnenen reflexionsseismischen und magnetischen Daten wurden mit dem Ziel interpretiert, die Entwicklung dieser Struktur während des Känozoikums besser zu verstehen. Basement-Hochlagen, welche die sedimentären Lagen bis zum frühen/mittleren Miozän deformieren, konnten identifiziert werden. In Kombination mit einer Ausdünnung der Kruste, wie sie von Grobys et al. (in Vorbereitung) für den zentralen Bounty Trog beobachtet wird, interpretieren wir diese Basement-Hochlagen als das Ergebnis magmatisch-tektonischer Aktivitäten, die im Miozän begann. Diese magmatisch-tektonische Aktivitäten reaktivitierten lithospherische Schwächezonen, welche während der kretazischen Riftphase angelegt wurden. Als Ursache der magmatisch-tektonischen Aktivitäten lassen sich Änderungen in den Plattenbewegungen im Süd-Pazifik diskutieren, die vor ~10 Ma zu Kompressionen entlang der Alpine Fault in Neuseeland führten.

Multichannel seismic (MCS) data from the Yaquina forearc basin off Peru reveal a complex distribution of gas and gas hydrate related reflections. Lateral variations of the reflection pattern at the assumed base of the gas hydrate stability zone in terms of continuity, amplitude, and signal attenuation underneath are observed, as well as the possible occurrence of paleo-bottom simulating reflectors (BSRs). Phase reversed reflections above the bottom simulating reflector point to free gas within the gas hydrate stability zone (GHSZ). To constrain the interpretation of the observed reflection pattern we calculated the velocity distribution along the MCS line from high-resolution ocean bottom hydrophone recordings with two independent methods. Heat flux values estimated on the basis of the velocity-depth functions increase with decreasing amplitude of the BSR and peak near chemoherms. These results suggest a model of the Yaquina Basin where free gas is trapped under parts of the BSR, and within the GHSZ, particularly under the seafloor and under an erosional unconformity. The hypothesis of a paleo-BSR that reflects the uplift of the base of the hydrate stability zone caused by the deposition of a particular sediment sequence is supported by the estimated heat flux values.

The Campbell Plateau and Chatham Rise are large submarine plateaux of continental origin forming part of the submarine New Zealand continent. Bounty Trough lies parallel to the former Gondwana subduction zone along the northern margin of Chatham Rise. At its western end, Bounty Trough (BT) connects with the Great South Basin (GSB). The whole region formed part of Gondwana until extension and subsequent seafloor spreading formed the Southern Ocean in the Late Cretaceous. Prior to the break-up of Gondwana, New Zealand was situated at the proto-Pacific plate boundary of Gondwana. Although the timing of break-up is relatively well defined, processes of break-up and the development of the continental fragments forming Campbell Plateau and Chatham Rise are not yet understood. It is expected that these processes played a key role in the development of Gondwanas plate boundary from a convergent margin to continental rifting. One model suggests that the Cretaceous rift evolved from an already existing back-arc basin, a proto-Bounty Trough. It may also be possible that the trough first developed as a rift system of the Southern Pacifics early opening as plate-kinematic reconstructions of the South Pacific region suggest.To investigate the evolution processes of these submarine plateaux, a geophysical and geolo-gical survey was conducted across the Campbell Plateau and Bounty Trough in 2003. The survey carried out two deep seismic transects with an ocean-bottom seismograph (OBS) spacing of 10-20 km in combination with a series of crustal multichannel seismic (MCS) reflection lines across the GSB and BT. The OBS records were bandpass-filtered and deconvolved. Magnetic and gravity data provide further constraints on the crustal models.The MCS profiles across the Bounty Trough show about 1.2 s (TWT) thick layered sediments with an incised valley. In most parts, basement can be identified in the reflection data, how-ever, in places only the OBS model allows discrimination of basem

MCS data from the Yaquina forearc basin off Peru reveal a complex distribution of gas and gas hydrate related reflections. Intricate lateral variations of the reflection pattern at the assumed base of the GHSZ in terms of continuity, reflection amplitude, and signal attenuation underneath are observed, as well as the occurrence of paleo-BSR. Phase reversed reflections at an erosional unconformity above the BSR indicate free gas within the GHSZ. In order to further constrain the interpretation of the observed reflection pattern we calculated the velocity distribution along the MCS line from high-resolution ocean bottom hydrophone recordings with two independent methods. The results from 2D-forward modelling and interactive velocity analysis show consistentresults. They exhibit a low velocity layer almost directly beneath the seafloor. Another low velocity layer with less than 1.5 km/s is present between the unconformity and the BSR.. In the vicinity and beneath prominent chemoherms, high velocities have been observed between the BSR and seafloor. Heat flux values calculated on the basis of the velocity-depth functions increase with decreasing amplitude of the bottom simulating reflector and peak near chemoherms. These results suggest a model of the Yaquina Basin where free gas is present under parts of the BSR, and within the hydrate stability zone, particularly under the sea floor and under the erosional unconformity. The higher interval velocities near and beneath the chemoherms are suspected to be caused either by thick gas hydrate lenses or a significant amount of precipitated carbonate within the sediment or a combination of both. The hypothesis of a paleo-BSR that reflects the uplift of the base of the GHSZ caused by the deposition of a particular sediment sequence is supported by the estimated heat flux values.

Einführung in das UntersuchungsgebietDas Campbell-Plateau ist der submarine Hauptbestandteil des neuseeländischen Mikrokontinents. Die relative Paläo-Position des größten ozeanischen Plateaus überwiegend kontinentalen Ursprungs läßt sich innerhalb des Gondwana-Gefüges sehr gut rekonstruieren. Vor dem Gondwana-Aufbruch lag Neuseeland an der proto-pazifischen Plattengrenze Gondwanas. Das Campbell-Plateau und der Chatham Rise waren verbunden mit Marie-Byrd-Land der Westantarktis. Der Bounty Trog trennt Campbell Plateau und Chatham Rise voneinander und besitzt vermutlich eine Verlängerung in das Great South Basin hinein. Allerdings sind die Krustenstruktur und die magmatisch-tektonische Entwicklung dieser Region weitgehend unbekannt, obwohl sie eine Schlüsselfunktion in der Entwicklung dieser Plattengrenze Gondwanas von einer konvergenten Grenze zu einem kontinentalen Rifting besitzen.Der Bounty Trog liegt parallel zur früheren Gondwana-Subduktionszone, die an der Nordseite des Chatham-Rise verlief. Es ist bisher unbekannt, ob das kreidezeitliche Rift aus einem bereits bestehenden Back-Arc-Becken, einem Proto-Bounty Trog, entstanden ist. Eventuell war der Trog ein nicht voll ausgebildetes Riftsystem der frühen Südpazifik-Öffnung, obwohl weder Ort noch Art des Ozean-Kontinent-Übergangs bekannt ist. Der Bounty Trog wird im Osten begrenzt von mindestens 83 Mio. Jahre alter ozeanischer Kruste (C34) und zeigt wenig Zeichen einer späteren Deformation, so daß angenommen werden kann, daß seine Entwicklung seit 83 Mio. Jahren abgeschlossen war.Experiment und DatenqualitätZur Untersuchung der Entwicklung eines solchen ozeanischen Plateaus kontinentalen Ursprungs wurde im Jahr 2003 ein Experiment mit dem Forschungsschiff F/S SONNE auf dem Bounty Trog und dem Campbell Plateau durchgeführt. Dabei wurden sowohl reflexions- als auch refraktionsseismische (mit insgesamt 45 Ozeanbodenseismometer-Stationen (OBS) auf zwei Profilen) Profildaten gesammelt. Der kombinierte Datensatz vom Boun

The Campbell-Plateau is a large submarine continental plateau lying to the southeastof New Zealand and separated from the landmass of New Zealand by a series ofdeep extensional sedimentary basins and geomorphologic deeps. The region (withNew Zealand) formed a part of Gondwana until extension and subsequent seafloorspreading formed the Southern Ocean at about 82 Ma. Although the timing of break-upis well defined, the processes of break-up and the development of the continentalfragment forming Campbell Plateau are not yet understood. To investigate theprocesses of evolution of submarine plateaux, a geophysical survey was conductedacross the Campbell Plateau in January and February 2003. The survey carried out aseismic (OBS) transect with a high density of OBSs (spacing ~ 10 - 20km) incombination with a series of crustal seismic reflection lines. It crossed the GreatSouth Basin and poorly known east-west trending inferred extensional basins on theCampbell Plateau and in the Bounty Trough. The large number of multicomponentOBS recordings enabled us to set up a densely spaced model based oncompressional as well as shear waves, which provides the possibility to revealinformation about lithologic properties as Poisson ratios. A preliminary model ofCampbell Plateau and Bounty Trough, based on travel-time inversion will bepresented here.

The lower boundary of the methane hydrate stability zone in continental margin sedi-mentsis often marked by a strong, phase reversed reflection subparallel to the seafloor,called the bottom simulating reflector (BSR). High resolution multichannel seismic(MCS) data from the Yaquina Basin offshore Peru at 8 deg S show a BSR that is vary-inglaterally in amplitude as well as in continuity. The amplitudes of the reflectionsabove the BSR also vary with the appearance of the BSR. Where the BSR is strong,the reflections above it are weaker compared to areas where the BSR is weak. Andalthough the strong part of the BSR is underlain immediately by strong reflections,reflections several hundred meters beneath the BSR appear weaker than those wherethe BSR is weak. This variation indicates significant heterogeneity in the distribu-tionof gas and gas hydrate in this area. Chemoherms observed at the Yaquina Basinsea floor indicate the presence of free gas in the sediments up to the seafloor. Thepresence of gas and gas hydrate within the sediment sequence significantly influencesthe P-wave velocity in the affected layers. Therefore a detailed analysis of velocityvariations enables to understand the apparently different conditions for the formationof gas hydrate along the BSR and the migration paths of the free gas. Ocean bot-tomseismometer (OBS) data from profiles coincident with the MCS data can providesuch detailed velocity depth information. Velocity analysis from OBS data included2D-ray tracing and 1D-interval-velocity analysis by means of DIX-inversion. In orderto find a trade-off between vertical resolution and minimization of errors caused bythe sensitivity of the DIX formula to velocity variations in thin layers, the data haveundergone a Kirchhoff wave-equation datuming and adjacent coherence filtering wasapplied to the data to eliminate the one sided travel path through the water columnof the OBS-observations. The derived velocity structure confirms the interpretation ofth

In high-resolution MCS data from Yaquina Basin off Peru we observed various intricate reflection patterns related to gas and gas-hydrate. The BSR variations classify theprofile into five areas: Where the BSR follows stratigraphy, it is disrupted by several faults but strong in amplitude. Reflection amplitudes from the overburden are reduced.Blanking occurs beneath the BSR. Continuing down slope where the BSR crosses stratigraphy the BSR amplitude decreases, reflections from above and beneath haveregular strength. Further down slope BSR continuity dissolves into a patchy occurrence with blanking beneath. Up slope the BSR continues with reduced reflectionamplitude and touches the sea floor. Towards coastline the BSR disappears completely.One of the most important tools to unravel the origin of the reflections is the high resolution velocity analysis of OBS data. On top of the MCS line a OBS/OBH profile hasbeen shot. Sources were two 1.7 l GI-guns (Sodera) with a peak frequency of 80 - 100 Hz. Eleven OBS/OBH of the GEOMAR type recorded with a sampling rate of 1 ms. Thisdata set allows a high resolution velocity analysis. Two different processing flows have been applied to the data. The data have undergone a Kirchhoff wave-equationdatuming and adjacent coherence filtering to eliminate the one sided travel path through the water column. Both datumed and not datumed seismograms have beenexamined with a semblance supported interactive velocity analysis. Data have also been analyzed with high and low resolution in depth in order to find an optimumtrade-off between vertical resolution and minimization of errors caused by sensitivity of the DIX' formula regarding velocity variations at thin layers. The data help tounderstand the reflection pattern in terms of gas-hydrate occurrence and dissociation, fluid migration and anisotropic permeability of sediments.

The last supercontinent fell into pieces with the break-up of Gondwana. In this context, the separation of the microcontinent of New Zealand from Antarctica is a jigsaw puzzle of many pieces. Its parts lay at the convergent margin of East Gondwana, which changed into a divergent margin within a geologically short time. That is why the microcontinent of New Zealand experienced different tectonic regimes and phases of the Wilson cycle. Although it is a good object of investigation due to its changing history, remarkably little is known about the submerged parts of the microcontinent. Knowledge of the magmatic-tectonic development of the submarine plateaux such as Campbell Plateau and Chatham Rise will improve the understanding of the processes that led to the late Gondwana break-up, and, in turn, lead to better reconstructions of East Gondwana, as Zealandia is a key piece in plate-kinematic reconstructions of this part of Gondwana.The central part of this thesis deals with the separation process of Zealandia from Antarctica leading to an improved reconstruction of New Zealand with emphasis on the submarine plateaux. Bounty Trough separating Chatham Rise from Campbell Plateau, and the Great South Basin separating Campbell Plateau from the South Island are investigated with seismic refraction and reflection methods. They are interpreted jointly with magnetic and gravity data. The results of crustal thickness modelling based on satellite gravity data are combined with existing information about crustal thickness of Zealandia. With these data, a crustal thickness grid is calculated which creates the basis for a novel technique for plate-kinematic reconstructions in areas of crustal thinning and in the absence of magnetic seafloor anomalies. This reconstruction consists of crustal balancing to compensate for extension within basins and troughs.The seismic refraction and reflection survey across the Bounty Trough shows a strongly thinned crust in the trough. Zones of high P

The last supercontinent fell into pieces with the break-up of Gondwana. In this context, the separation of the microcontinent of New Zealand from Antarctica is a jigsaw puzzle of many pieces. Its parts lay at the convergent margin of East Gondwana, which changed into a divergent margin within a geologically short time. That is why the microcontinent of New Zealand experienced different tectonic regimes and phases of the Wilson cycle. Although it is a good object of investigation due to its changing history, remarkably little is known about the submerged parts of the microcontinent. Knowledge of the magmatic-tectonic development of the submarine plateaux such as Campbell Plateau and Chatham Rise will improve the understanding of the processes that led to the late Gondwana break-up, and, in turn, lead to better reconstructions of East Gondwana, as Zealandia is a key piece in plate-kinematic reconstructions of this part of Gondwana.The central part of this thesis deals with the separation process of Zealandia from Antarctica leading to an improved reconstruction of New Zealand with emphasis on the submarine plateaux. Bounty Trough separating Chatham Rise from Campbell Plateau, and the Great South Basin separating Campbell Plateau from the South Island are investigated with seismic refraction and reflection methods. They are interpreted jointly with magnetic and gravity data. The results of crustal thickness modelling based on satellite gravity data are combined with existing information about crustal thickness of Zealandia. With these data, a crustal thickness grid is calculated which creates the basis for a novel technique for plate-kinematic reconstructions in areas of crustal thinning and in the absence of magnetic seafloor anomalies. This reconstruction consists of crustal balancing to compensate for extension within basins and troughs.The seismic refraction and reflection survey across the Bounty Trough shows a strongly thinned crust in the trough. Zones of high P

The last supercontinent fell into pieces with the break-up of Gondwana. In this context, the separation of the microcontinent of New Zealand from Antarctica is a jigsaw puzzle of many pieces. Its parts lay at the convergent margin of East Gondwana, which changed into a divergent margin within a geologically short time. That is why the microcontinent of New Zealand experienced different tectonic regimes and phases of the Wilson cycle. Although it is a good object of investigation due to its changing history, remarkably little is known about the submerged parts of the microcontinent. Knowledge of the magmatic-tectonic development of the submarine plateaux such as Campbell Plateau and Chatham Rise will improve the understanding of the processes that led to the late Gondwana break-up, and, in turn, lead to better reconstructions of East Gondwana, as Zealandia is a key piece in plate-kinematic reconstructions of this part of Gondwana.The central part of this thesis deals with the separation process of Zealandia from Antarctica leading to an improved reconstruction of New Zealand with emphasis on the submarine plateaux. Bounty Trough separating Chatham Rise from Campbell Plateau, and the Great South Basin separating Campbell Plateau from the South Island are investigated with seismic refraction and reflection methods. They are interpreted jointly with magnetic and gravity data. The results of crustal thickness modelling based on satellite gravity data are combined with existing information about crustal thickness of Zealandia. With these data, a crustal thickness grid is calculated which creates the basis for a novel technique for plate-kinematic reconstructions in areas of crustal thinning and in the absence of magnetic seafloor anomalies. This reconstruction consists of crustal balancing to compensate for extension within basins and troughs.The seismic refraction and reflection survey across the Bounty Trough shows a strongly thinned crust in the trough. Zones of high P