Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The interpretation of high-resolution 2D marine seismic profiles together with the analysis of sea-bottom cores allowed a stratigraphic and structural framework of the Provence continental shelf to be proposed. The integration of onshore and offshore stratigraphy, structure and geomorphology provided new insights into Messinian paleotopography and paleohydrography. A geological map of the offshore Provence continental shelf, isobath map of the base Plio-Quaternary surface are presented for the first time in this area. The base Plio-Quaternary surface is a polyphased unconformity that is composed of deep canyons developed by fluvial erosion during the Messinian event, and wave-cut surfaces formed during post-Messinian transgressions. The study evidenced a deep, E-W-trending canyon (Bandol canyon) connected to the head of the Cassidaigne canyon, and filled with up to 600 m-thick Plio-Quaternary deposits. The development of canyons on the Provence margin during the Messinian event was dominantly controlled by the lithology and structure of pre-Messinian formations. A map of the Messinian paleo-drainage network is proposed to explain the presence of deep canyons in the Eastern area and the lack of incision in the Western area. An underground karst drainage scheme is proposed, linked with the current submarine Port-Miou spring.
ISSN: 0264-8172

insu-01009592
https://hal-insu.archives-ouvertes.fr/insu-01009592
https://hal-insu.archives-ouvertes.fr/insu-01009592/document
https://hal-insu.archives-ouvertes.fr/insu-01009592/file/Mar-Pet-Tassy.pdf
DOI : 10.1016/j.marpetgeo.2014.05.001

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Selected high-resolution seismic-reflection profiles and multibeam bathymetry acquired along the convergent Ecuador margin during the ATACAMES cruise on onboard the R/V L’Atalante (Jan.15–Feb.18, 2012) allow a preliminary evaluation of the neotectonic development and stratigraphic evolution of the margin based on the sismo-stratigraphic analysis of Quaternary sediment preserved on the margin shelf and upper slope. We present three major preliminary results. (1) The evolution of the Esmeraldas, Guayaquil and Santa Elena canyons. The head of the Esmeraldas canyon is the location of a continuous significant sediment transport. The Guayaquil canyon shows several episodes of deposition and incision. Aggrading sedimentation pattern in the canyon records several changes in relative sea-level. The subsidence of the Gulf of Guayaquil probably contributes to the good preservation of the canyon filling stages. The Santa Elena canyon is controlled by a SW–NE trending normal fault. (2) Variations of sediment accumulation and relative vertical motions are shown along-strike the shelf edge. Offshore the uplifted Manta peninsula, a pronounced subsidence of the shelf edge is documented by sedimentary clinoforms that have deposited in a morphological reentrant, and have migrated upslope testifying of a local subsidence meanwhile the adjacent La Plata Island area underwent uplift. In the Esmeraldas canyon area, a local uplift of the shelf is documented. (3) Two neotectonic fault systems with a possible transcurrent component are imaged across the shelf edge and upper margin slope offshore Jama, and Cape Galera. This possible transcurrent motion could be related to the reactivation of ancient faults of the upper plate by the subduction. These preliminary results indicate that the ATACAMES data set has a strong potential to evaluate the spatial and temporal contribution of tectonic and climate changes on the structural development and stratigraphic evolution of the Ecuador continental margin.
ISSN: 0025-3235

insu-01131151
https://hal-insu.archives-ouvertes.fr/insu-01131151
DOI : 10.1007/s11001-014-9231-y

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Reef positions record the interaction between eustasy and tectonics, and have been used worldwide to characterize vertical deformations of upper-plates at different time-scales and constrain the seismic behavior of megathrusts. Along the Lesser Antilles volcanic arc, high-resolution marine geophysical data were collected on the 2–20 km wide eastern Martinique reef platform to reconstruct its stratigraphic and morphologic history, and understand the influence of local normal faulting, volcanism and plate-scale subduction processes on Holocene and Late Pleistocene reef development. The subsiding Martinique platform's stratigraphy is composed of multiple superimposed sea-level highstand deposits separated by subaerial exposure surfaces of sea-level low stands. The carbonate platform consists of two laterally-extensive carbonate units (unit U2 overlying unit U3) that extend to the platform edge to a depth of − 95 m MSL (mean sea level), and form two morphologic terraces, M2 and M3 respectively. The landward portion of unit U2 is partially overlain between 0 and − 60 m MSL by the living reef tract U1. The current reef is composed of a landward fringing reef, a lagoon and a seaward barrier reef, the latter forming a double-bank barrier around the Caravelle Peninsula. In near-shore multi-channel seismic profiles, a distinct reflector at ~− 35 m MSL, probably a subaerial exposure surface E1, separates the reef sequence formed during the last transgression from a Pleistocene fossil reef tract forming unit U2. Offshore of Mount Pelée volcano (Late Pleistocene), the Holocene reef did not develop above unit U2, whose upper surface is incised by channels and apparent sinkholes. During the Holocene transgression, the possibility of excessive turbidity due to volcanic activity may have inhibited reef development in this area. The un-dated unit U2 probably developed 120–130 ka ago during the last interglacial (MIS 5.5) + 6 m MSL highstand as thick, extensive reefs deposited all along the Lesser Antilles arc. Due to subsidence, MIS 5.5 reefs are not represented by onshore facies, except along the southern Sainte Anne Peninsula where normal faulting and uplift balances island-scale subsidence. Based on unit U2's present elevation and assuming an MIS 5.5 age and + 6 m MSL sea level, Martinique has subsided at maximum 0.3 m/ky, likely due to subduction processes that question the coupling state of the megathrust.
ISSN: 0025-3227

hal-01307036
https://hal.archives-ouvertes.fr/hal-01307036
DOI : 10.1016/j.margeo.2015.08.001

Éditeur(s) : HAL CCSD Société géologique de France
Résumé : International audience
Guadeloupe island (West French Indies) is one of the twenty islands that compose the Lesser Antilles arc, which results from the subduction of the Atlantic ocean plate beneath the Caribbean one. The island lies in a complex volcano-tectonic system and the need to understand its geological context has led to numerous on- and offshore geophysical investigations. This work presents a compilation and the processing of available, on-land, airborne and marine, gravity and magnetic data acquired during the last 40 years on Guadeloupe islands and at the scale of the Lesser Antilles arc. The overall dataset provides new Bouguer and reduced to the pole magnetic anomaly maps at the highest achievable resolution. Regionally, the main central negative gravity trend of the arc allows defining two subsident areas. The first one is parallel to the arc direction (~N160°E) to the north, whereas the second unexpected southern one is oriented parallel to oceanic ridges (N130°E). Along the Outer arc, the long wavelength positive anomaly is interpreted, at least along the Karukera spur, as an up-rise of the volcanic basement in agreement with the seismic studies. To the NE of Guadeloupe, the detailed analysis of the geophysical anomalies outlines a series of structural discontinuities consistent with the main bathymetric morphologies, and in continuity of the main fault systems already reported in this area. Based on geophysical evidences, this large scale deformation and faulting of the Outer arc presumably primarily affects the Atlantic subducting plate and secondarily deforms the upper Caribbean plate and the accretion prism, as evidenced in bathymetry as well as on the islands. At the scale of Guadeloupe island, combined gravity and magnetic modeling has been initiated based on existing interpretation of old seismic refraction profiles, with a general structure in three main layers. According to our geophysical anomalies, additional local structures are also modeled in agreement with geological observations: i) the gravity and magnetic signals confirm an up-rise of the volcanic basement below the limestone platforms outcropping on Grande-Terre island ; ii) the ancient volcanic complexes of Basse-Terre island are modeled with high density and reverse magnetized formations; iii) the recent volcanic centre is associated with formations consistent with the low measured density and the underlying hydrothermal system. The E-W models coherently image a NNW-SSE depression structure in half-graben beneath Basse-Terre island, its western scarp following the arc direction in agreement with bathymetric and seismic studies to the north of the island. The so-defined depressed area, and particularly its opening in half-graben toward the SW, is interpreted as the present-day front of deformation of the upper plate, associated with the recent volcanic activity on and around Guadeloupe. Based on this regional deformation model, perspectives are given for further integrated investigation of key targets to address the internal structure and evolution of the Lesser Antilles arc and Guadeloupe volcanic system.
EISSN: 1777-5817

hal-00853352
https://hal.archives-ouvertes.fr/hal-00853352
DOI : 10.2113/gssgfbull.184.1-2.77

Éditeur(s) : Elsevier
Résumé : We present new results from the MARADJA'03 cruise depicting the geological structures offshore central and western Algeria. Using swath bathymetry and seismic reflection data, we map and discuss the offshore limits of the Internal Zones corresponding to relics of the AIKaPeCa domain that drifted and collided the African plate during the Miocene. We identify large reverse faults and folds that reactivate part of these limits and are still active today. The morphology of the westernmost NE-SW margin suggests a former strike-slip activity accommodating a westward block translation responsible for the shift of the Internal Zones towards the Moroccan Rif.
Nous présentons les résultats récents de la campagne MARADJA'03, qui visent à mettre en évidence les structures géologiques dans le domaine marin au nord-ouest de l'Algérie. Grâce aux données de bathymétrie multifaisceau et de sismique réflexion, nous cartographions et discutons les limites en mer des Zones internes correspondant aux reliques du domaine AlKaPeCa qui a dérivé, puis est entré en collision avec la plaque africaine au Miocène. De grandes failles inverses et plis, actifs dans le champ de contrainte actuel, réactivent certaines de ces limites. La marge ouest-algérienne, orientée NE¿SW, indique la présence d'une ancienne activité en décrochement ayant accommodé la translation des Zones internes vers l'ouest.
Comptes Rendus Geoscience (1631-0713) (Elsevier), 2006 , Vol. 338 , N. 1-2 , P. 80-91

Droits : 2005 Académie des sciences Published by Elsevier SAS
http://archimer.ifremer.fr/doc/2006/publication-1211.pdf
DOI:10.1016/j.crte.2005.11.009
http://archimer.ifremer.fr/doc/00000/1211/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The Maguelone shore extends along the northern coast of the Gulf of Lions, west of the Rhone Delta and east of high-gradient coastal streams that have provided most of the clastic sediments to the Gulf of Lions margin since the early Miocene. This 10 km-wide area is constituted by a small coastal watershed (15 km long) in low-lying carbonate hills, a kilometre-wide marsh, a sandy beach barrier and a shoreface experiencing local low sedimentation rates. This onshore-offshore transition zone is a key area to understand the relationships between erosion, by-pass, deposition and preservation processes. Unlike the neighbouring Rhone deposits that display numerous thick deltaic sequences related to a continuous sediment flux, the Maguelone shore exhibits peculiar sedimentary bodies. The analysis of about 250 km of new VHR seismic profiles acquired over the study area, 9 short cores and outcrops data allowed us to determine the three-dimensional high-resolution geometry of the coastal system tracts from Quaternary to present-day. This revealed dominant denudation processes in the Upstream catchments associated with the formation of incised valleys during Quaternary lowstands. In addition, this study investigates the erosion and deposition mechanisms controlled by littoral hydrodynamics that have been taken place on this shore since the last transgression. In particular, metre-high and hundreds of metre-long sandy bodies constructed by alongshore hydrodynamics were identified and their effect on the morphodynamics of the whole littoral system is discussed. The Maguelone shore can be used as an experimental study for onshore/offshore dynamics under the influence of microtidal wave/current hydrodynamics and very low river-derived sediment flux during a eustatic cycle. Geometry of system tracts across flood plain to shoreface is usually considered to be controlled by relative sea-level changes, and is successfully analysed with 2D sequence stratigraphy cross-shore models. It is observed that in areas like the Maguelone shore, traditional sequence stratigraphy methods might not be fully relevant and need to integrate alongshore hydrodynamical processes.
ISSN: 0025-3227

hal-00421060
https://hal.archives-ouvertes.fr/hal-00421060
DOI : 10.1016/j.margeo.2009.06.008

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The Taiwan area, where the Philippine Sea Plate collides with Eurasia, is one of the most seismically active areas in the world and has been consequently struck repeatedly by destructive earthquakes. To better constrain the occurrence of large earthquakes, we have conducted two cruises in 2012 and 2013 from which five piston, gravity and box-cores were retrieved from selected sites in targeted areas that contain continuous and accurate turbidite deposition offshore eastern Taiwan. Forty-seven turbidite layers deposited between 675 BC and 2012 AD have been described in the cores with facies varying from silty clay to coarse sand. We modeled each turbidite layer using the sedimentation rate deduced from radiocarbon age measurements performed on planktonic foraminifers. Precise dating based on 210Pb–137Cs chronology provided ages for the XXth century turbidites. Coring sites' locations, biotic association within turbidites beds and seismic calibration over the instrumental period, suggest that earthquakes are the most likely triggering mechanisms of turbidity currents over the last 2700 years. Calibration of correlations between turbidites and instrumental earthquakes allowed us to determine the minimum magnitude of recorded events (Mw = 6.8) and the maximum distance between the epicenter and the slope failure. Turbidites' synchroneity between cores has been tested but results showed that this criterion cannot be used in our study area because of the high level of seismicity, i.e., a M > 6.8 earthquake recurrence interval much smaller than the uncertainty on radiocarbon ages. The excellent accuracy of dating allows correlating all the turbidites deposited since 1920 with instrumental earthquakes. For each core, we established a return time ranging between 112 and 147 years for the period pre-1900 and ~ 27 and 34 years for the period post-1900. The discrepancy between pre-1900 and post-1900 recurrence either suggests, that slope stability varies, with higher slope instability after 1900 possibly due to increased sediment delivery by rivers.
ISSN: 0040-1951

hal-01467627
https://hal.archives-ouvertes.fr/hal-01467627
DOI : 10.1016/j.tecto.2016.04.030

Éditeur(s) : HAL CCSD Geological Society of London
Résumé : Permo-Triassic rift basins offer important hydrocarbon targets along the Atlantic margins. Their fill is dominated by continental red beds, comprising braided fluvial, alluvial fan, aeolian, floodplain and lacustrine facies. These relatively lightly explored basins span both the Atlantic and Tethyan domains and developed above a complex basement with inherited structural fabrics. Sparse data in offshore regions constrain understanding of depositional geometries and sedimentary architecture, further impeded by their deep burial beneath younger strata, combined with the effects of later deformation during continental breakup. This paper provides results from a multidisciplinary analysis of basins along the Atlantic margin. Regional seismic and well data, combined with geochemical provenance analysis from the European North Atlantic margins, are integrated with detailed outcrop studies in Morocco and Nova Scotia. The research provides new insights into regional basin tectonostratigraphic evolution, sediment fill, and reservoir distribution, architecture and quality at a range of scales. Regional seismic profiles, supported by key well data, indicate the presence of post-orogenic collapse basins, focused narrow rifts and low-magnitude multiple extensional depocentres. Significantly, Permo-Triassic basin geometries are different and more varied than the overlying Jurassic and younger basins. Provenance analysis using Pb isotopic composition of detrital K-feldspar yields new and robust controls on the sediment dispersal patterns of Triassic sandstones in the NE Atlantic margin. The evolving sedimentary architecture is characterized by detailed sedimentological studies of key outcrops of age equivalent Permian-Triassic rifts in Morocco and Nova Scotia. The interplay of tectonics and climate is observed to influence sedimentation, which has significant implications for reservoir distribution in analogue basins. New digital outcrop techniques are providing improved reservoir models, and identification of key marker horizons and sequence boundaries offers a potential subsurface correlation tool. Future work will address source and seal distribution within the potentially petroliferous basins.
Petroleum Geology: From Mature Basins to New Frontiers Proceedings of the 7th Petroleum Geology Conf

hal-00590618
https://hal.archives-ouvertes.fr/hal-00590618

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The contourite depositional system (CDS) along the southwestern Iberian Margin (SIM), within the Gulf of Cadiz and offshore areas of western Portugal bear the unmistakable signal of Mediterranean Outflow Water (MOW) exiting the Strait of Gibraltar. This locality records key information concerning the effects of tectonic activity on margin sedimentation, the effects of MOW dynamics on Atlantic circulation, and how these factors may have influenced global climate. Over the last four decades, numerous studies have been conducted on the late Miocene, Pliocene and Quaternary sedimentary stacking pattern of Neogene basins along the SIM for both academic and resources exploration purposes. However, understanding of the region rests primarily on basic seismic stratigraphy calibrated with limited data from only a few exploration wells. The Integrated Ocean Drilling Program (IODP) Expedition 339 recently drilled five sites in the Gulf of Cadiz and two sites on the western Iberian margin. The integration of core and borehole data with other geophysical databases leads us to propose a new stratigraphic framework. Interpretation of IODP Exp. 339 data along with that from industry sources and onshore outcrop analysis helps refine our understanding of the SIM's sedimentary evolution.We identify significant changes in sedimentation style and dominant sedimentary processes, coupled with widespread depositional hiatuses along the SIM within the Cadiz, Sanlucar, Doñana, Algarve and Alentejo basins. Following the 4.5 Ma cessation of a previous phase of tectonic activity related to the Miocene–Pliocene boundary, tectonics continued to influence margin development, downslope sediment transport and CDS evolution. Sedimentary features indicate tectonic pulses of about 0.8–0.9 Ma duration with a pronounced overprint of ~ 2–2.5 Ma cycles. These more protracted cycles relate to the westward rollback of subducted lithosphere at the convergent Africa-Eurasia plate boundary as its previous NW–SE compressional regime shifted to a WNW–ESE direction. Two major compressional events affecting to the Neogene basins at 3.2–3 Ma and 2–2.3 Ma help constrain the three main stages of CDS evolution. The stages include: 1) the initial-drift stage (5.33–3.2 Ma) with a weak MOW, 2) a transitional-drift stage (3.2–2 Ma) and 3) a growth-drift stage (2 Ma-present time) with enhanced MOW circulation into the Atlantic and associated contourite development due to greater bottom-current velocity. Two minor Pleistocene discontinuities at 0.7–0.9 Ma and 0.3–0.6 Ma record the effects of renewed tectonic activity on basin evolution, appearing most prominently in the Doñana basin. Several discontinuities bounding major and minor units appear on seismic profiles. Quaternary records offer the clearest example of this, with major units of about 0.8–0.9 Ma and sub-units of 0.4–0.5 Ma. Sedimentation is controlled by a combination of tectonics, sediment supply, sea-level and climate. This research identifies time scales of tectonic controls on deep-marine sedimentation, specifically over periods of 2.5–> 0.4 Ma. Shorter-term climatic (orbital) mechanisms control sedimentation at time scales of ≤ 0.4 Ma. The role of bottom water circulation and associated processes in shaping the seafloor and controlling the sedimentary stacking pattern on continental margins has to be seriously reconsidered in future multidisciplinary studies. This is not only because of the common occurrence of sandy contourite deposits in deep water setting and their economic interest for hydrocarbon exploration, but principally because they archive the heartbeat of the interior Earth and therefore have important sedimentary and paleoceanographic implications.
ISSN: 0025-3227

hal-01356166
https://hal.archives-ouvertes.fr/hal-01356166
DOI : 10.1016/j.margeo.2015.09.013

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The detailed morphology and internal structure of the Calabrian accretionary wedge and adjacent Eastern Sicily margin are imaged in unprecedented detail by a combined dataset of multi-beam bathymetry and high-resolution seismic profiles. The bathymetric data represent the results of 6 recent marine geophysical surveys since 2010 as well as a compilation of earlier surveys presented as a 2 arc-sec (60 m) grid. Several distinct morpho-tectonic provinces are identified including: the deeply incised Malta–Hyblean Escarpment, numerous submarine canyons, broad regions of relatively flat seafloor dominated by fields of sediment waves, the gently undulating anticlinal fold-and-thrust belts of the external Calabrian accretionary wedge and the adjacent portion of the Western Mediterranean Ridge. The Calabrian arc can be divided into 4 domains (from SE to NW): 1) the undeformed Ionian abyssal plain, 2) the external evaporitic wedge, 3) the internal clastic wedge, 4) the Calabrian backstop (Variscan crystalline basement). The Calabrian accretionary wedge can also be divided laterally into two major lobes, the NE- and the SW lobes, and two minor lobes. The kinematics of the limit between the two major lobes is investigated and shown to be sinistral in the external (evaporitic) wedge. A network of radial slip lines within the southernmost external wedge unequivocally demonstrate ongoing dextral displacement of a rigid indenter (representing the corner of the clastic wedge) into the evaporitic wedge thereby confirming the geodynamic model of an active lateral slab tear fault here off eastern Sicily. The slab tear produces a series of major sub-parallel dextral strike-slip faults offshore Mt. Etna and south of the Straits of Messina consistent with the relative motions between Calabria and the Peloritan domain (NE Sicily). Abundant strike-slip faulting, and wide-spread folding and thrusting observed throughout the entire accretionary wedge, indicate regional shortening between the Ionian abyssal plain (foreland) and the Calabrian–Peloritan backstop caused by active subduction.
ISSN: 0012-821X

hal-01523990
https://hal.archives-ouvertes.fr/hal-01523990
DOI : 10.1016/j.epsl.2016.12.020

Éditeur(s) : American Geophysical Union
Résumé : The Fairway Ridge is a buried continental structure that separates the Fairway Basin from the New Caledonia Basin. The proposed Cretaceous age of the Fairway Basin has remained highly hypothetical to date. Deep offshore petroleum exploration wells revealed well-dated Mesozoic carbonaceous sedimentary rocks in the Taranaki Basin at the southern end of the Aotea Basin. In this paper we use geophysical data to confirm the continuity of the 2000 km long Fairway-Aotea Basin connecting New Caledonia to New Zealand and prove its early Late Cretaceous age. Analysis of seismic reflection profiles together with newly compiled gravity and magnetic maps reveals Late Cretaceous NE–SW trending lineaments projecting northeastward from major Tasman Sea fracture zones and the Bellona Trough, which demonstrate that the opening of the Fairway-Aotea Basin predates the opening of the Tasman Sea. This result combined with observations of the Mesozoic regional geology suggests that the Lord Howe, Fairway, and Norfolk ridges are part of a remnant late Early Cretaceous continental arc, which was fragmented into three pieces by the late Early to early Late Cretaceous. This event might be contemporaneous with a plate motion change between the Gondwana and Pacific plates and/or the arrival of the Hikurangi plateau in the subduction zone around 105 Ma, which caused the cessation of subduction along this plate boundary. We interpret either of those two events as being possible trigger events for the post–Early Cretaceous fragmentation of the eastern Gondwana margin in a slab retreat process.
Geochemistry Geophysics Geosystems - G3 (1525-2027) (American Geophysical Union), 2009-12 , Vol. 10 , N. 12 , P. 1-24

Droits : 2009 American Geophysical Union
http://archimer.ifremer.fr/doc/2009/publication-7322.pdf
DOI:10.1029/2009GC002612
http://archimer.ifremer.fr/doc/00000/7322/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Forty years after the image of the Mediterranean transformed into a giant salty lake was first conceived, the fascinating history of the Messinian Salinity Crisis (MSC) still arouses great interest across a large and diverse scientific community. Early outcrop studies which identified severe palaeoenvironmental changes affecting the circum-Mediterranean at the end of the Miocene, were followed by investigations of the marine geology during the 1950s to 1970s. These were fundamental to understanding the true scale and importance of the Messinian event. Now, after a long period of debate over several entrenched but largely untested hypotheses, a unifying stratigraphic framework of MSC events has been constructed. This scenario is derived mainly from onshore data and observations, but incorporates different perspectives for the offshore and provides hypotheses that can be tested by drilling the deep Mediterranean basins.The MSC was an ecological crisis, induced by a powerful combination of geodynamic and climatic drivers, which had a great impact on the subsequent geological history of the Mediterranean area, and on the salinity of the global oceans. These changed the Mediterranean's connections with both the Atlantic Ocean and the freshwater Paratethyan basins, causing high-amplitude fluctuations in the hydrology of the Mediterranean. The MSC developed in three main stages, each of them characterized by different palaeoenvironmental conditions. During the first stage, evaporites precipitated in shallow sub-basins; the MSC peaked in the second stage, when evaporite precipitation shifted to the deepest depocentres; and the third stage was characterized by large-scale environmental fluctuations in a Mediterranean transformed into a brackish water lake.The very high-resolution timescale available for some Late Miocene intervals in the Mediterranean makes it possible to consider environmental variability on extremely short time scales including, in some places, annual changes. Despite this, fundamental questions remain, some of which could be answered through new cores from the deepest Mediterranean basins. Improvements in seismic imaging and drilling techniques over the last few decades make it possible to plan to core the entire basinal Messinian succession for the first time. The resulting data would allow us to decipher the causes of this extreme environmental change and its global-scale consequences.
ISSN: 0025-3227

hal-01115664
https://hal.archives-ouvertes.fr/hal-01115664
DOI : 10.1016/j.margeo.2014.02.002

Éditeur(s) : Elsevier Sci Ltd
Résumé : The eastern Demerara Plateau offshore French Guiana was surveyed in 2003 during the GUYAPLAC cruise (multibeam bathymetry and acoustic imagery, 6-channel seismic reflection and 3.5 kHz echo-sounding). The data show the "post-transform" Cenozoic that the series located on the outer part of the plateau (below c. 2000 m) contain at least twelve stacked mass transport deposits (MTDs) that have recorded a history of large-scale slope failure, as well as two main normal fault sets that provide possible pathways for upward fluid migration through the series, reaching at high as the uppermost MTDs. Seabed data show that the area above the failures is characterized by circular-to-elongate (slope-parallel) depressions interpreted as fluid seeps (pockmarks), some of them have been modified by along slope currents. We suggest that the development of the MTDs to results from the combinaiton of the presence of fluid overpressure at depth the geometry of the margin's deep structure, in particular the existence of a 'free borderlateral border' on the outermost plateau. Our results also emphasise the role of stratigraphic decollements within the Cenozoic series.
Marine And Petroleum Geology (0264-8172) (Elsevier Sci Ltd), 2013-09 , Vol. 46 , P. 287-303

Droits : 2013 Elsevier Ltd. All rights reserved.
http://archimer.ifremer.fr/doc/00157/26850/25316.pdf
DOI:10.1016/j.marpetgeo.2013.06.010
http://archimer.ifremer.fr/doc/00157/26850/