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Topography growth and sediment fluxes in active subduction margin settings are poorly understood. Geological record is often scarce or hardly accessible as a result of intensive deformation. The Hawke Bay forearc basin of the Hikurangi margin in New Zealand is well suited for studying morphstructural evolution. It is well preserved, partly emerged and affected by active tectonic deformation during Pleistocene stage for which we have well dated series and well-known climate and eustasy. The multidisciplinary approach, integrating offshore and onshore seismic interpretations, well and core data, geological mapping and sedimentological sections, results in the establishment of a detailed stratigraphic scheme for the last 1.1 Ma forearc basin fill. The stratigraphy shows a complex stack of 11 eustasy-driven depositional sequences (20, 40 and 100 ka periodicity). These sequences are preserved in sub-basins that are bounded by active thrust structures. Each sequence is characterized by important changes of the paleoenvironment that evolves between the two extremes of the glacial maximum and the interglacial optimum. Thus, the Hawke Bay forearc domain shows segmentation in sub-basins separated by tectonic ridges during sea level lows that become submerged during sea level highs. Over 100 ka timescale, deformation along active structures together with isostasy are responsible of a progressive migration of sequence depocenters towards the arc within the sub-basins. Calculation of sediment volumes preserved for each of the 11 sequences allows the estimation of the sediment fluxes that transit throughout the forearc domain during the last 1.1 Ma. Fluxes vary from c. 3 to c. 6 Mt.a-1. These long-term variations (100 ka to 1 Ma timescale ranges) are attributed to changes in the forearc domain tectonic configuration (strain rates and active structure distribution). They reflect the ability of sub-basin to retain sediments. Short-term variations of fluxes (

The cored sediments sampled by R/V Marion Dufrense are mostly muds consisting mainly of quartz, feldspar, illite, chlorite + kaolinite and calcite. Authigenic carbonates mainly composed of aragonite, calcite, dolomite and associated with Fe-montmorillonite and pyrite occur in core samples collected from station MD-052911 (22 degrees 15.6' N, 119 degrees 51.0' E) at 2137-2140 cm and 2237-2240 cm depth which may be formed via sulfate reduction by CH4. In general Illite/Quartz intensity ratios of the sediments show little variation with core depth indicating the relatively constant abundance of illite in the source rock on Taiwan. The cored sediments have higher average Al2O3, Sigma FeO and MgO but lower SiO2, Na2O, and CaO contents when compared with upper continental crust (UCC). High field strength elements (Zr, Hf, Y, Nb and Ta) are also depleted in the cored sediments. CaO, Sr, Mn and Pb in the core samples collected from station MD-052912 (22 degrees 21.5' N, 119 degrees 48.5' E) tend to decrease with depth which may be essentially related to the decrease of biogenic CaCO3 with core depth. The La/Th, La/Sc, Th/Sc ratios of the cored sediments are similar to those of UCC, however the (La/Yb)(N) ratios of the cored sediments are higher. The cored sediments display similar REE patterns with LREE enrichment and negative Eu anomaly reflecting a felsic nature of the source rock which can also be identified in the La-Th-Sc plot. The chemistry of the sediments can be deduced using a mixing model involved four end members i.e., shale, greywacke, quartzite and limestone.

A study of the distribution of diagenetic alterations and their impact on reservoir-quality evolution in four deep-water turbidite successions (Cretaceous to Eocene) from basins in active (foreland) and passive margins revealed the impact of tectonic setting, depositional facies, and changes in the relative sea level. Diagenetic modifications encountered in the turbiditic sandstones from the passive margin basins include dissolution and kaolinitization (kaolin has δ18OV-SMOW = +13.3‰ to +15.2‰; δDV-SMOW = -96.6‰ to -79.6‰) of framework silicates, formation of grain coating chloritic and illitic clays, cementation by carbonates and quartz, as well as the mechanical and chemical compaction of detrital quartz. Kaolinitization, which is most extensive in the lowstand systems tracts, is attributed to meteoric-water flux during major fall in the relative sea level. Preservation of porosity and permeability in sandstones from the passive margin basins (up to 30% and 1 Darcy, respectively) is attributed to the presence of abundant rigid quartz and feldspar grains and to dissolution of carbonate cement as well as mica and feldspars. Diagenetic modifications in turbidites from the foreland basins include carbonate cementation and mechanical compaction of the abundant ductile rock fragments, which were derived from fold-thrust belts. These diagenetic alterations resulted in nearly total elimination of depositional porosity and permeability. The wide range of δ13CV−PDB values of these cements (about -18‰ to +22‰) in passive margin basins is attributed to input of dissolved carbon from various processes of organic matter alterations, including microbial methanogenesis and thermal decarboxylation of kerogen. The narrower range of δ13CV−PDB values of these cements (about -2‰ to +7‰) in the foreland basins suggests the importance of carbon derivation from the dissolution of carbonate grains. The generally wide range of δ18O values (about -17‰ to -1‰) of the carbonate cements reflect the impact of oxygen isotopic composition of the various fluid involved (including marine depositional waters, fluxed meteoric waters, evolved formation waters) and the wide ranges of precipitation temperatures. Results of this study are anticipated to have important implication for hydrocarbon exploration in deep-water turbidites from passive and active margin basins and for pre-drilling assessment of the spatial and temporal distribution of reservoir quality in such deposits.

The Northern Andes differ from the Central Andes by the presence of oceanic terranes accreted in the upper Cretaceous and Paleogene. As a consequence, the Andes of Ecuador comprise accreted oceanic terranes to the West (Costa, Cordillera Occidental), and the South American continental margin to the East (Cordillera Real, Subandean zone and Oriente basin).This work aims to characterize the quartz-rich clastic sediments deposited during successive accretions and to propose a model for the chain uplift and erosion. In addition, this aims to verify the hypothesis of Guillier et al. (2001) et Jaillard et al. (2002), which propose that the relief of the Andes of Ecuador does not result from tectonic shortening of the continental margin, as in the Central Andes, but from the addition, by accretion and underplating during oceanic terranes accretions, of buoyant oceanic crustal material, exerting an Archimedes force responsible for the chain uplift, which then induced the reactivation of the erosion, and the deposition of quartz-rich clastic sediments, that seal the accretions.We studied sandstones and conglomerates of Campanian to Eocene age, coeval with the accretion and underplating of oceanic terranes, in order to determine the tectonic consequences of these processes on the tectonic behaviour of the Ecuadorian continental margin, specially on the Occidental Cordillera and the Real Cordillera, but also on the back-arc and fore-arc zones. Therefore, we analyzed : (1) the paleodepths of deposition of the syntectonic sediments, and the erosional discontinuities due to each accretion ; (2) the position of the paleo-shoreline and of the marine sedimentation on either side of the emergent margin ; (3) the topographic gradient between the source zones and the depocentres, expressed by the grain size variations of the sediments ; and (4) the exhumation of the source zones, through the petrographic evolution of the studied clastic sediments. Three basins of the Occidental Cordillera were studied in detail: the Cuenca basin to the South, and those of Saquisilí and Apagua in the Central part of Ecuador.The vertical succession of sedimentary environments in the studied basins shows the presence of major erosive unconformities defining four main depositional sequences, and points out the accretion periods. These accretions are: (1) Late Campanian (≈ 75–72 Ma), (2) Late Maastrichtian (≈ 69–65 Ma), and (3) Late Paleocene (≈ 58–56 Ma) in age. A last tectonic event of Late Eocene age (Bartonian - Priabonian) was well recorded throughout the margin. From South to North of the Occidental Cordillera, the 4 sequences evidence, except for the Maastrichtian, a jerked shallowing upward trend of the paleodepths of deposition from the Campanian to the Eocene. This study also evidences the retreat of the paleoshoreline during the upper Cretaceous - Paleogene interval. Indeed, the sedimentary basins of the Cordillera Occidental are younger, as they migrate to the west, and also northward. As a matter of fact, the southern Cuenca basin is infilled by middle Campanian to Paleocene p.p. deposits, the sediments of the Saquisilí basin are of Early Maastrichtian to early Middle Eocene age, and the Apagua basin contains eocene sediments. It is worth to note that farther Northwest, the La Cubera basin was infilled by sediments of Paleocene to Late Eocene age.Each accretion corresponds to an increasing grain size of sandstones and conglomerates, in the western basins (Cordillera Occidental and Costa) as well as in the Eastern zones (Subandean Zone and Oriente basin), except for the upper Maastrichtian accretion, which did not provoke an increase of the grain size in the sediments, but an erosional hiatus and a noticeable change in the source zones.In the Cuenca, Saquisilí and Apagua basins, a coarsening upward trend is recorded within each sequence (Campanian, Paleocene and Eocene), as well as in the succession of the sequences, confirming both the steepening of the margin paleoslope, and the uplift of the source area, essentially constituted by the Cordillera Real. Within each sequence, the increasing paleoslope is expressed by the rapid evolution from sandstones to conglomerates, which announces the tectonic event responsible for the overlying unconformity. For the same time-spans, similar evolutions are recorded, although in a more distal manner, on the Coast and in the eastern zones of Ecuador. Since the Cretaceous until the Paleogene, the mineral assemblages of the clastic sediments of the Cordillera Occidental show a three-stage evolution : (1) surrection and exhumation of the Cordillera Real, from the Campanian to the Paleocene, and to a minor extent until the upper Eocene ; (2) increasing amount, from the Paleocene to the Eocene, of volcanic and sedimentary lithic fragments deriving from the deformation and erosion of the previously accreted terrains ; and (3) resumption of the magmatic arc activity from upper Eocene onward, indicated by the enrichment in plagioclase crystals. During stage 1, the sediments show a clear enrichment in stable minerals and lithic grains (mono- and polycrystaline quartz) at the expense of feldspars, thus reflecting a greater maturity of Paleogene sediments, with respect to those of the latest Cretaceous. At that time, the main source area was the Cordillera Real. From upper Paleocene on (stage 2), the increasing amount of lithic fragments deriving from the oceanic terranes shows that the deformed and eroded zone extends westward, and eventually includes the accreted terranes.In addition, this analysis allowed to point out two original results. The rectangle-shaped basins of the Cordillera Occidental (Cuenca, Saquisilí, Apagua, La Cubera) show tectonically active borders corresponding to major, NNE-trending dextral strike-slip faults, which reactivates accretionary sutures, and important subsidence rates, which suggest they are pull apart basins. We observe also an increase of deposition rates through time, suggesting an increasing instability of these basins located on the accretion sutures. The creation of these basins seems to coincide with the accretion of oceanic terranes, that would have occurred, therefore, in a dextral transpressive regime. The northward migration of these basins through time remains, however, to be explained. The eastern areas of Ecuador are classically interpreted as representing the flexural back arc basin (foredeep) of the Andean chain since the upper Cretaceous. Nevertheless, our study shows that, at a regional scale: (1) the hiatuses and erosions are more important at the foot of the Cordillera Real than to the East ; (2) the thicknesses of the Campanian to Eocene deposits increase from West to the East ; and (3) the Maastrichtian, Paleocene and Eocene sequences seem to retrograde toward the West. This set of observations point out that this part of the margin underwent uplift, rather than flexural subsidence. We propose that the Andes of Ecuador were built up by isostatic uplift associated with the successive accretion and underplating, beneath the margin, of crustal oceanic material of relatively weak density. These terranes would have generated an Archimedes force, responsible for the isostatic surrection of the margin following each accretion. In this model, the viscous reaction of the uplifted and flexured lithosphere would had accentuated its curvature radius, allowing the retrogradation of back-arc clastic deposits toward the chain, and explaining the observed lag-time of the sedimentary response in the eastern areas., Les Andes du Nord diffèrent des Andes centrales par la présence de terrains océaniques accrétés au Crétacé supérieur et Paléogène. Ainsi les Andes d'Equateur comprennent des terrains océaniques accrétés à l'Ouest (Côte, Cordillère Occidentale), et la marge continentale de l'Amérique du Sud à l'Est (Cordillère Royale, zone Subandine et bassin Oriente). Cette étude a pour but de caractériser les dépôts de sédiments détritiques quartzeux mis en place au cours des accrétions successives et de bien cadrer un modèle de surrection de la chaîne et de son érosion. On espère ainsi apporter des éléments pour tester le modèle de Guillier et al. (2001) et Jaillard et al. (2002) selon lequel le relief des Andes d'Equateur résulte non du raccourcissement tectonique de la marge continentale comme c'est le cas des Andes centrales, mais de l'addition en profondeur, par accrétion et sous-placage lors des accrétions de terrains océaniques, de matériel crustal océanique. Celui-ci exercerait une poussée d'Archimède responsable de la surrection de la chaîne, puis de l'érosion et du dépôt de sédiments détritiques quartzeux, qui scellent ces accrétions.Dans ce but, nous avons étudié les grès et conglomérats d'âge Campanien à Eocène, contemporains de l'accrétion et du sous-placage des terrains océaniques, afin de déterminer les conséquences tectoniques de ces processus sur le comportement tectonique de la marge continentale de l'Équateur, en particulier sur la Cordillère Occidentale et la Cordillère Royale, mais aussi sur les zones d'arrière-arc et d'avant-arcPour cela, on a analysé : (1) les paléo-profondeurs des dépôts de sédiments syntectoniques, et les discontinuités érosives liées à chaque accrétion ; (2) la position des paléo-rivages et des l'aires de sédimentation marine de chaque côté de la marge émergée ; (3) le gradient topographique entre zones sources et zones de dépôt, traduit par la granulométrie des dépôts ; et (4) l'exhumation des zones sources, au travers de l'évolution pétrographique des sédiments clastiques étudiés. L'étude a porté sur trois bassins de la Cordillère Occidentale : le bassin de Cuenca au Sud, et ceux de Saquisilí et d'Apagua au Centre de l'Equateur.La succession verticale des milieux sédimentaires dans les bassins étudiés montre la présence de discordances érosives majeures définissant 4 grandes séquences de dépôt, et encadrant les périodes d'accrétion. Ces accrétions peuvent ainsi être datées : (1) du Campanien supérieur (≈ 75–72 Ma), (2) du Maastrichtien supérieur (≈ 69–65 Ma), (3) du Paléocène supérieur (≈ 58–56 Ma). Un dernier événement tectonique de l'Éocène supérieur (Bartonien - Priabonien) est bien ressenti sur la marge. Du Sud au Nord de la Cordillère Occidentale ces 4 séquences indiquent, mise à part celle du Maastrichtien, une diminution globale de la paléo-profondeur du Campanien à l'Eocène. Cette étude met également en évidence le recul de la paléo-ligne de côte au cours du Crétacé supérieur–Paléogène. En effet, les bassins sédimentaires de la Cordillère Occidentale sont de plus en plus jeunes, d'une part à mesure que l'on s'éloigne de la Cordillère Royale (vers l'Ouest), et d'autre part lorsqu'on se déplace vers le Nord. Ainsi, le bassin de Cuenca au Sud montre un remplissage du Campanien moyen à Paléocène p.p., les dépôts du bassin de Saquisilí vont du Maastrichtien inférieur à la base de l'Éocène moyen, et le bassin d'Apagua contient des sédiments éocènes. Notons que plus au Nord-Ouest, le bassin de la Cubera est rempli de sédiments d'âge Paléocène à Eocène supérieur.À chaque accrétion correspond une augmentation de la granulométrie des grès et des conglomérats, dans les bassins occidentaux (Cordillère Occidentale et côte) comme dans les zones orientales (Zone subandine et bassin Oriente). Seule l'accrétion du Maastrichtien supérieur ne se traduit pas par l'augmentation de la granulométrie, mais par une lacune d'érosion et un changement de zones sources.Dans les bassins de Cuenca, de Saquisilí et d'Apagua, la taille des grains augmente vers le haut, au sein de chaque séquence (Campanien, Paléocène et Eocène), mais aussi d'une séquence à l'autre, confirmant l'accentuation de la paléo-pente de la marge et la surrection de la zone source, constituée essentiellement par la Cordillère Royale. L'augmentation de la paléo-pente se traduit aussi, au sein de chaque séquence, par le passage rapide des grès à des conglomérats en réponse à l'événement tectonique responsable de la discontinuité sus-jacente. Les mêmes évolutions sont observées aux mêmes périodes, mais enregistrées de façon plus distale, sur la côte et dans les zones orientales de l'Equateur. Au cours du Crétacé–Paléogène, l'étude des cortèges de minéraux détritiques des sédiments clastiques de la Cordillère Occidentale montre une évolution en trois étapes : (1) surrection et exhumation de la Cordillère Royale, du Campanien au Paléocène, et dans une moindre mesure jusqu'à l'Éocène supérieur ; (2) abondance croissante, du Paléocène à l'Eocène, de fragments lithiques volcaniques et sédimentaires dérivant de la déformation et de l'érosion des terrains préalablement accrétés, et (3) reprise de l'activité de l'arc magmatique à partir de l'Éocène supérieur-Oligocène inférieur marqué par un enrichissement en plagioclases. L'étape 1 montre un enrichissement des sédiments en grains minéraux et lithiques de plus en plus stables (quartz mono- et polycristallin) au détriment des feldspaths, qui reflète une plus grande maturité des sédiments du Paléogène par rapport à ceux du Crétacé terminal. La source principale est alors la Cordillère Royale. À partir du Paléocène supérieur (étape 2), l'augmentation progressive des fragments lithiques issus de couvertures océaniques montre que la zone déformée et soumise à l'érosion s'élargit, et inclut les terrains accrétés.De plus, cette analyse a permis de mettre en évidence deux résultats supplémentaires. Les bassins de la Cordillère Occidentale (Cuenca, Saquisilí, Apagua et La Cubera), présentent une géométrie rectangulaire, des bordures actives correspondant à des failles décrochantes dextres orientées NNE réactivant les sutures, et une subsidence importante, qui suggèrent qu'il s'agit de bassins en «pull apart». On note de plus une augmentation de leur taux de sédimentation avec le temps, suggérant une instabilité croissante de ces bassins installés sur les sutures des accrétions. La création de ces bassins semble coïncider avec les accrétions de terrains océaniques, qui se seraient donc effectuées en contexte transpressif. Leur migration vers le Nord dans le temps reste cependant à expliquer. Les zones orientales sont classiquement interprétées comme un bassin flexural d'avant-pays de la chaîne andine depuis le Crétacé supérieur. Cependant, notre étude montre qu'à l'échelle du bassin : (1) les hiatus et les érosions sont plus importants au pied de la Cordillère Royale qu'à l'Est ; (2) l'épaisseur des dépôts campaniens à éocènes augmente d'Ouest en Est ; et (3) les séquences du Maastrichtien, du Paléocène et de l'Eocène sont rétrogradantes en direction de l'Ouest. L'ensemble de ces observations indique donc que la marge est en surrection, plutôt qu'en subsidence. Nous proposons donc un modèle de construction de la chaîne andine par surrection isostatique liée à l'introduction successive sous la marge, par accrétion et sous-placage, de matériel crustal océanique de densité relativement faible. Ces terrains auraient causé une poussée d'Archimède responsable de la surrection isostatique de la marge après chaque accrétion. Dans ce modèle, après chaque surrection, la réaction visqueuse de la lithosphère soulevée et flexurée aurait abouti à accentuer le rayon de courbure de la lithosphère, permettant la rétrogradation des dépôts clastiques d'arrière-arc en direction de la chaîne, et expliquant le délai observé de la réponse sédimentaire dans ces zones orientales.

In southeast Anatolia, there are number of tectonomagmatic units in the Kahramanmaraş-Malatya-Elazig region that are important in understanding the geological evolution of the southeast Anatolian orogenic belt during the Late Cretaceous. These are (a) metamorphic massifs, (b) ophiolites, (c) ophiolite-related metamorphics and (d) granitoids. The granitoids (i.e. Göksun-Afşin in Kahramanmaraş, Doganşehir in Malatya and Baskil in Elazig) intrude all the former units in a NE-SW trending direction. The granitoid in Göksun-Afşin (Kahramanmaraş) region is mainly composed of granodioritic and granitic in composition. The granodiorite contains a number of amphibole-bearing mafic microgranular enclaves of different sizes, whereas the granite is intruded by numerous aplitic dikes. The granitoid rocks have typical calcalkaline geochemical features. The REE- and Ocean ridge granite-normalized multi-element patterns and tectonomagmatic discrimination diagrams, as well as biotite geochemistry suggest that the granitoids were formed in a volcanic arc setting. The K-Ar geochronology of the granitoid rocks yielded ages ranging from 85.76 ± 3.17 to 77.49 ± 1.91 Ma. The field, geochemical and geochronological data suggest the following Late Cretaceous tectonomagmatic scenario for southeast Anatolia. The ophiolites were formed in a suprasubduction zone tectonic setting whereas the ophiolite-related metamorphic rocks formed either during the initiation of intraoceanic subduction or late-thrusting (~90 Ma). These units were then overthrust by the Malatya-Keban platform during the progressive elimination of the southern Neotethys. Thrusting of the Malatya-Keban platform over the ophiolites and related metamorphic rocks was followed by the intrusion of the granitoids (88-85 Ma) along the Tauride active continental margin in the southern Neotethys. © Springer-Verlag 2005. Firat University Scientific Research Projects Management Unit: MMF2001.13 YDABC¸ AG-199Y011 Acknowledgments This research was partly supported by TÜBİTAK (Scientific and Technical Research Council of Turkey, Project Number: YDABC¸ AG-199Y011) and Division of the C¸ ukurova University Scientific Research Projects (MMF2001.13). Michel Delaloye is thanked for allowing me to use XRF and K–Ar facilities in the Mineralogy Department at Geneva University (Switzerland). Volker Höck is thanked for free access to microprobe facilities in the Geology Department at Salzburg University (Austria). Utku Bag^ cı and Tamer Rızaog^ lu are thanked for their field assistancy. Osman Parlak also acknowledges the financial support from the Turkish Academy of Sciences, in the frame of the Young Scientist Award Program (TÜBA-GEBİP). Nurdane İlbeyli and Yann Rolland are thanked for reviewing the first version of the manuscript. Thanks are due to Prof. Alastair Robertson who reviewed the revised version of the present manuscript.

The sedimentary architecture of active margin basins, including back-arc basins, is known only from a few end-members that barely illustrate the natural diversity of such basins. Documenting more of these basins types is the key to refining our understanding of the tectonic evolution of continental margins. This paper documents the sedimentary architecture of an incipient back-arc basin 200 km behind the active Hikurangi subduction margin, North Island, New Zealand. The Wanganui Basin (WB) is a rapidly subsiding, Plio-Pleistocene sedimentary basin located at the southern termination of the extensional back-arc basin of the active Central Volcanic Region (TVZ). The WB is asymmetric with a steep, thrust-faulted, outer (arc-ward) margin and a gentle inner (craton-ward) margin. It contains a 4-km-thick succession of Plio-Pleistocene sediments, mostly lying offshore, composed of shelf platform sediments. It lacks the late molasse-like deposits derived from erosion of a subaerial volcanic arc and basement observed in classical back-arc basins. Detailed seismic stratigraphic interpretations from an extensive offshore seismic reflection data grid show that the sediment fill comprises two basin-scale mega-sequences: (1) a Pliocene (3.8 to 1.35 Ma), sub-parallel, regressive bpre-growthQ sequence that overtops the uplifted cratonward margin above the reverse Taranaki Fault, and (2) a Pleistocene (1.35 Ma to present), divergent, transgressive, bsyn-growthQ sequence that onlaps: (i) the craton-ward high to the west, and (ii) uplifted basement blocks associated with the high-angle reverse faults of the arc-ward margin to the east. Along strike, the sediments offlap first progressively southward (mega-sequence 1) and then southeastward (mega-sequence 2), with sediment transport funnelled between the craton- and arc-ward highs, towards the Hikurangi Trough through the Cook Strait. The change in offlap direction corresponds to the onset of arc-ward thrust faulting and the rise of the Axial Ranges at ca 1.75 Ma, resulting in 5100­5700 m of differential subsidence across the fault system. Sedimentation has propagated south- to southeast-ward over the last 4 Myrs at the tip of successive back-arc graben, volcanic arcs and the associated thermally uplifted parts of the North Island, following the southward migration of the Hikurangi subduction margin. Subsidence occurred by mantle flow-driven flexure, the result of active down-drag of the lithosphere by locking of the Hikurangi subduction interface and sediment loading. The WB is considered to be a proto-back-arc basin that represents the intermediate stage of evolution of an epicratonic shelf platform, impacted by active margin processes.

22 pages, 10 figures, 1 table., The lateral ending of the South Shetland Trench is analysed on the basis of swath bathymetry and multichannel seismic profiles in order to establish the tectonic and stratigraphic features of the transition from an northeastward active to a southwestward passive margin style. This trench is associated with a lithospheric-scale thrust accommodating the internal deformation in the Antarctic Plate and its lateral end represents the tip-line of this thrust. The evolutionary model deduced from the structures and the stratigraphic record includes a first stage with a compressional deformation, predating the end of the subduction in the southwestern part of the study area that produced reverse faults in the oceanic crust during the Tortonian. The second stage occurred during the Messinian and includes distributed compressional deformation around the tip-line of the basal detachment, originating a high at the base of the slope and the collapse of the now inactive accretionary prism of the passive margin. The initial subduction of the high at the base of the slope induced the deformation of the accretionary prism and the formation of another high in the shelf—the Shelf Transition High. The third stage, from the Early Pliocene to the present-day, includes the active compressional deformation of the shelf and the base-of-slope around the tip-line of the basal detachment, while extensional deformations are active in the outer swell of the trench., We would like to thank the Commander, officers and crew of the B/O Hespérides for their help during the ANTPAC 97-98 cruise. We are grateful for the help of the U.G.B.O. technicians participating in the cruise. The expert help of Emilia Litcheva and Javier Maldonado, who processed the MCS and the swath bathymetry, is appreciated. We also acknowledge the work of Jean Sanders in reviewing the English text and A. Carbó for the release of the Lanzada software. The Spanish “Comisión Interministerial de Ciencia y Tecnología (CICYT)” provided financial support through research project ANT99-0817.

La datation des zircons détritiques de l'unité de la Boghen permet d'attribuer un âge post-liasique à cet ensemble, autrefois considéré comme le " socle anté-permien " de la Nouvelle-Calédonie. Ce complexe est formé d'un ensemble volcanosédimentaire et terrigène à caractère distal, reposant directement sur une croûte océanique ou de bassin marginal incomplète. Compte tenu de ses caractères sédimentologiques, de l'existence d'un métamorphisme de haute pression d'âge Jurassique (environ 150 Ma) et de son association au complexe volcanosédimentaire d'arc de la Chaîne centrale, il est possible d'interpréter cette unité comme un prisme d'accrétion mis en place au Jurassique le long de la marge active Est-Gondwanienne. Le spectre d'âge des zircons détritiques permet d'assigner le système d'arcs permo-mésozoïques Sud-Est-Gondwanien et l'Antarctique comme sources principales de la fraction détritique. Abstract Radiochronological dating of detrital zircon extracted from the Boghen terrane metasediments allows a Jurassic age to be assigned. This terrane was formerly considered as the "pre-Permian basement" of New Caledonia. Its sedimentological features, its Late Jurassic high-pressure metamorphism (ca 150 Ma) and its association with the arc-related volcano-sedimentary complex of the Central Chain Terrane indicate that the Boghen terrane was an accretionary complex formed during the Jurassic period along the East-Gondwana active margin. The age spectrum of detrital zircons is consistent with a derivation from the Permian-Mesozoic Southeast-Gondwana arc system and the Antarctic continent.

Stratigraphie analysis , together with discovery of faunas and of microfaunas , and study of depositional and environmental patterns in the Indus formations, Ladakh , allow characterization of several lithostratigraphic units. Despite fa- cies variations they have been identified along more than 100 km from West to East, and mapped on a 1/ 125. 000 scale . The overall structure consists of a dissymetric synclinorium, faulted by northward-trending reverse faults . It results from two major deformations. Microstructural analysis indicates shortening along a direction close to N 10 . Both deformation and metamorphism increase from N to S . This has been related to a Northward-trending retrothrusting phase. The geodynamic history of the Indus basin is the one of an active margin involved in an intercontinental collision. By the end of late Albian imes , a sedimentary basin makes its appearance in front of the magmatic arc linked to the South Tibetan active margin. This basin brings to mind the inner fore-arc of the present days Andean margin. From upper Cretaceous until Lower Eocene time , open sea conditions prevail in the southern part of the basin , whereas thick torrential and fluviatile formations originating from the erosion of the Ladakh magmatic arc , are deposited in its Northern part. After the Middle Eocene, a general regression follows the collision between South Tibet and India ; sedimentation becomes c ontinental throughout the whole basin; its corresponds to the superposition of several imbricated detrital forms. The continuing Northward drifting of India causes a strong tightening resulting in deformations and metamorphism in the Indus inner fore arc series , which finally undergo overthrusting by the outer fore - arc ' s formations, the Indus suture zone is now completely closed.; L'analyse stratigraphique, la découverte de faunes et microfaunes et l 'étude des modes et milieux de dépôts permettent de distinguer plusieurs unités lithostratigraphiques, qui malgrè quelques variations de faciès, se suivent latéralement d'Ouest en Est et ont pu être cartées au 1/125.000e. La structure d ' ensemble en synclinorium dissymétrique affecté de failles inverses à vergence nord résulte de deux phases de plissements majeures . L 'analyse microstructurale permet d 'estimer une direction de raccourcissement proche de N10. L 'importance des déformations et l 'intensité du métamorphisme décroissent toutes deux du Sud vers le Nord. Ceci peut être mis en relation avec un rétrochevauchement vers le Nord . L'histoire de l évolution du bassin de l'Indus est celle d'une marge active prise dans une collision intercontinentale. En avant 'un arc magmatique, mis en place le long de la marge active sud tibétaine , s 'individualise dès l'Albien supérieur un bassin semblable au "fore arc" interne des marges andines actuelles. Pendant toute la fin du Crétacé et jusqu'à l'Eocène inférieur, des conditions marines franches régnent au Sud du bassin, tandis qu ' au Nord les produits terrigènes issus du démantèlement du batholite ladakhi constituent d 'importants cônes torrentiels ou fluviatiles. A partir de l 'Eocène moyen, consécutivement à la collision des blocs indien et sud tibétain s'observe une régression généralisée; la sédimentation devient continentale sur tout le bassin , et correspond à la superposition de cônes alluviaux plus ou moins distaux . La dérive vers le Nord du bloc continental indien se poursuivant un serrage important règle les déformations et le métamorphisme qui affectent les séries du bassin de l'Indus; celles- ci finissent par être chevauchées par les formations du fore -arc externe : la cicatrice de l'Indus est alors définitivement structurée.

An ignimbritic sheet interlayered in Paleogene (Oligo-Miocene?) continental deposits in the Northern Ranges of Majorca is made up of rhyolites and K-rich rhyolites, of presumed calc-alkaline origin. This volcanic activity is interpreted in the framework of an active margin with development of marginal basins during Tertiary times in the Westerm Mediterranean, in accordance with pre-established models, Una hoja ignimbrítica interlaminada en depósitos continentales paleogénicos (¿Oligo-Mioceno?) en la sierra norte de Mallorca está formada por riolitas y riolitas ricas en potasio, con un presunto origen calco-alcalino. Esta actividad volcánica es interpretada en un marco del margen activo con desarrollo de cuencas marginales durante el Terciario en el oeste mediterráneo, según los modelos preestablecidos.