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International audience; Haiti lies along the North Caribbean plate boundary, marked by two major left-lateral strike-slip faults. A southwest-verging Trans-Haitian fold-and-thrust belt (FTB), mostly affecting tertiary carbonate platform, developed in central Haiti between the two faults, south of the Massif du Nord and the San Juan–Los Pozos Fault Zone, as a result of north-south shortening. The large NW-SE antiformal Gonâve Island and Ridge mark the southwest termination of the FTB as it encountered the Southern Peninsula and Enriquillo-Plantain Garden Fault Zone. We show that this collision resulted in a tightening of the deformed wedge and thrust faults rooted deeper into the crust, leading to a transition from thin-skinned to thick-skinned tectonics in the Pliocene. These short- (3–6 km) and long- (15–30 km) wavelength folding deformations are temporally distinct in the north and more concomitant in the south, where compressional thin-skinned deformation is still active. The thick-skinned shortening was mostly expressed during the Quaternary, as shown by the formation of folds and uplift of terraces between 1.7 Ma and today. This thick-skinned detachment is characterised by a stronger imprint of strike-slip component, dragging the FTB to a more E-W direction in its northwest and southeast extremities. Understanding of the fault zone geometry of the recent 2010 Haiti earthquake (M = 7.2) could be reconsidered in the light of this tectonic transition.

Transpressive deformation at the northern Caribbean plate boundary is accommodated mostly by two major strikeslip faults, but the amount and location of accommodation of the compressional component of deformation is still debated. We collected marine geophysical data including multi-beam bathymetry and multichannel seismic reflection profiles along this plate boundary around Hispaniola, in the Jamaica Passage and in the Gulf of Gonâve. The data set allows us to image the offshore active strike-slip faults as well as the compressional structures. We confirm that the Enriquillo-Plantain-Garden Fault Zone (EPGFZ) in the Jamaica Passage has a primary strike-slip motion, as indicated by active left-lateral strike-sliprelated structures, i.e.: restraining bend, asymmetrical basin, en echelon pressures ridges and horsetail splay. Based on topographic cross-sections across the EPGFZ, we image a very limited compressional component, if any, for at least the western part of the Jamaica Passage. Toward the east of the Jamaica Passage, the fault trace becomes more complex and we identify adjacent compressional structures. In the Gulf of Gonâve, distributed folding and thrust faulting of the most recent sediments indicate active pervasive compressional tectonics. Estimates of shortening in the Jamaica Passage and in the Gulf of Gonâve indicate an increase of the compressional component of deformation towards the east, which nonetheless remains very small compared to that inferred from block modelling based on GPS measurements

International audience; The Southern Peninsula of Haiti is a seismically active east-west trending transpressive mountain range with elevations over 2 km. Present-day deformation is mainly partitioned along the left-lateral Enriquillo-Plantain Garden Fault Zone (EPGFZ) and associated oblique reverse faults and/or folds. The configuration of these faults, their respective timing, and the role of structural heritage on their development is poorly understood. To address these questions we present the results of extensive field campaigns, combined with satellite imagery interpretation and published data, which allows us to constrain the Cenozoic evolution of the Southern Peninsula. Our results show a polyphase tectonic history consisting of three major tectonic events: 1) Maastrichtian to early Paleocene crustal-scale folding that developed coevally with predominantly north to northeast dipping thrusts, resulting in uplift and erosion of the Cretaceous sedimentary cover in large parts of the Southern Peninsula. 2) Early Miocene uplift and erosion, which was strongest in the southwestern part of the peninsula and 2 decreased eastwards, did not affect the Massif de la Selle. Uplift is most likely unrelated to strike-slip activity but resulted from folding in response to NE-SW shortening that possibly reactivated older, predominantly N-to NE-dipping thrusts. 3) Late Miocene to present-day deformation and uplift. Spatially distributed strike-slip started during the late Miocene and became progressively focused along the EPGFZ in the latest Miocene. Oblique and thrust faults locally postdate strike-slip activity from the Pliocene onward. Increase in compressional deformation from west to east is reflected by a change in structural style, with predominantly strike-slip faults in the west and transpressional faults in the east, the latter possibly rooted on the EPGFZ at depth. Paleo-stresses associated with a strike-slip regime are at a significantly high angle to the trace of the EPGFZ, indicating that the EPGFZ is a mechanically weak fault.

A recent study suggested that Indian monsoonal proxies commonly used in the Arabian Sea, in general productivity proxies, could be impacted by changes in the Atlantic overturning rate (AMOC) throughout a control on the nutrient delivery into the euphotic zone. This oceanic mechanism could lead to a misunderstanding between the Indian summer monsoon (SM) and orbital forcing and could confuse a direct comparison with other archives derived from other monsoonal sub-systems (such as East-Asian or African records). Here we analyze three independent proxies (bromine, foraminifera assemblages and grain size) extracted from a marine sediment core (MD04-2861) covering the last 310 ka, and retrieved in the northern Arabian Sea near the Makran margin, an area influenced by summer and winter Indian monsoon. The grain size proxy deals with the regional continental climate through fluvial and eolian processes. It cannot be linked to changes in nutrient content of AMOC and present the same phase relationship (timing) than the other SM proxies. This demonstrates that the productivity signals (Bromine) in the northern Arabian Sea are mainly controlled by SM dynamics and not AMOC modulated nutrients at orbital scale changes. We thus build a multi-proxy record of SM variability (i.e. SM stack) using statistical tools (principal component analysis) further compiled on an age model constructed independently from orbital tuning. We find that strong SM lag by 9 ± 1 ka the NH summer insolation maximum (minimum of precession, June 21 perihelion and obliquity maximum) in the precession band, and by 6 ± 1.3 ka in the Obliquity band. These results are consistent with previous studies based on marine and terrestrial records in both Indian and Asian regions, except Asian speleothems. Our study supports the hypothesis that internal climate forcing (decreased ice volume together with the increase of latent heat export from the southern Indian Ocean) set the timing of strong Indo-Asian summer monsoons within both the precession and obliquity cycle. The external forcing (direct sensible heating) initiate monsoonal circulation. Strong Indian winter monsoon (WM) occurs between ice maxima and northern hemisphere sensible heat minima, indicating that both act to strengthen WM circulation. The summer and winter monsoons are in antiphase in the precession band suggesting that the two systems are dynamically linked.

This study focuses on the exceptionally high occurrence of Orbulina suturalis and morphotypes very close to Praeorbulina in Late Glacial sediments from the Northern Arabian Sea. The genus Praeorbulina has been described by Blow (1956) as an ancestor of Orbulina universa. Our study is based on the analysis of three sediment cores retrieved in the Gulf of Oman (KS01, MD04-2849, and MD04-2861), covering the Late Pleistocene (last 30 ka CAL-BP). Planktonic foraminiferal assemblages were investigated and revealed that this remarkable abundance of Orbulina suturalis, and numerous specimens morphologically close to Praeorbulina, occurs during a short time interval roughly representing the Last Glacial Maximum. One AMS 14C date was obtained on a monospecific sample of Praeorbulina-like specimens, giving an age of 19 CAL-ka BP, which confirms the Late Glacial age and unreworked character of this population. In this paper, we discuss the morphological similarities relating the observed Praeorbulina-like specimens to the genera Orbulina and Praeorbulina. We will also discuss the period of occurrence of these specimens and the potential environmental changes that may have caused their atypical morphology.

Julien Bourget, Sebastien Zaragosi, Nadine Ellouz-Zimmermann, Nicolas Mouchot, Thierry Garlan, Jean-Luc Schneider, Valentine Lanfumey and Sigfried Lallemant

article The main sediment depocenter along the Oman margin is the Al Batha turbidite system that develops in the Gulf of Oman basin. It is directly connected to the wadi Al Batha, and forms a typical sand and mud rich point source system that acts as regional sediment conduit and feeds a ~1000 km 2 sandy lobe. The Al Batha lobe depositional architecture has been investigated in detail using very high-resolution seismic, multibeam echosounder data and sediment cores. Several scales of depositional architecture can be observed. The Al Batha lobe is composed of several depositional units, made of stacked elementary sediment bodies (thinner than 5 m) that are each related to a single flow event. The lobe is connected to the feeder system through a channel-lobe transition zone (CLTZ) that extends on more than 25 km. The lobe can be divided into proximal, middle and distal lobe areas. The proximal lobe is an area of erosion and by-pass with small axial feeder channels that rapidly splay into several small distributaries. They disappear in the mid-lobe area where deposits consist of vertically stacked tabular to lens-shaped sediment bodies, with a lateral continuity that can exceed 10 km. The distal lobe fringe shows a classical facies transition towards thin- bedded basin plain deposits. Sub-surface deposits consist of sandy turbidites and hyperpycnites, interbedded with fine-grained deposits (thin turbidites, hyperpycnites, or hemipelagites). Although these distal deposits are mainly related to flow transformations and concentration evolution, they highlight the importance of flooding of the wadi Al Batha on the sediment transfer to the deep basin. The thick sandy hyperpycnites recovered in such a distal area are also possibly related to the initial properties of gravity flows, in relation to the flooding characteristics of mountainous desert streams.

A geophysical and geological survey (CHAMAK) has been carried out on the Makran accretionary wedge off Pakistan in order to understand the structure of the margin and the recent sedimentary processes in this self-maintaining prism disconnected from the modern Indus inputs (Qayyum et al., 1997; Gaedicke et al., 2002a; Schluter et al., 2002). Morphostructural analysis, based on the interpretation of bathymetric data and backscatter imagery, as well as a 3.5 kHz echo-character mapping, allow us to distinguish three structural domains, from north to south, where sedimentary processes differ: (1) the accretionary wedge to the north, (2) the trench and (3) the northern Murray Ridge at the seaward edge of the trench. The accretionary wedge is cut by canyons responsible for an important erosion of the prism especially in the eastern part of the wedge. Within the trench, sediments transported by the canyons generate sediment waves and are transported westward, parallel to the E–W axis of the trench. The eastern part of the abyssal plain is eroded by strong turbidity currents whereas important sediment deposition occurs in the western part of the abyssal plain, as a consequence of a decrease in the current energy. Nearly no mass transport deposits are recognized in the study area except near the ridges forming the accretionary wedge. Small-scale slope failure scars are described. The prevalence of turbiditic processes and the existence of a morphological barrier formed by the Murray Ridge allow the confinement of turbidites within the trench. Migrating sediment waves seem to be common sedimentary structures in this setting. These features might be produced by important velocity decrease of turbidity currents when reaching the trench.

International audience; Multibeam bathymetry data and multichannel seismic reflection profiles have been collected at the end of 2012 along the Enriquillo-Plantain-Garden Fault Zone (EPGFZ) in the Jamaica Passage, between Jamaica and Hispaniola. Analysis of the data set reveals the tectonic evolution and the stratigraphic complexity of the northern Caribbean boundary. Stratigraphic correlations with previous marine and on land studies are proposed to place the identified seismic sequences in their regional tectonic history. Two distinct crustal domains are interpreted. Typical stratigraphic sequences for the rifted blocks of the Eastern Cayman Trough margin are identified in five basins of the Jamaica Passage, highlighting the eastward limit of the Cayman Trough margin. These inherited basins are deformed and folded during a first phase of compression that could correspond to the regional tectonic rearrangement recorded in the early Miocene (about 20 Ma). A distinct crustal domain that we propose to relate to the Carib Beds (Caribbean typical reflectors A′′,B′′ and V) is identified in the southern part of the Jamaica Passage, indicating that the Caribbean Large Igneous Province could extend up to the extreme northeast part of theLower Nicaragua Rise. The left-lateral EPGFZ currently cuts acrosstwo pre-existing basins, the Morantand Matley basins. During the activity of the EPGFZ, these basins are deformed and folded indicating a second phase of compression. In contrast, the Navassa basin, located in the middle of the Jamaica Passage, results from the strike-slip motion of the EPGFZ and is interpreted as an asymmetricalbasin bordered by the EPGFZonly on its northern side

We explored the submarine portions of the Enriquillo–Plantain Garden Fault zone (EPGFZ) and the Septentrional–Oriente Fault zone (SOFZ) along the Northern Caribbean plate boundary using high-resolution multibeam echo-sounding and shallow seismic reflection. The bathymetric data shed light on poorly documented or previously unknown submarine fault zones running over 200 km between Haiti and Jamaica (EPGFZ) and 300 km between the Dominican Republic and Cuba (SOFZ). The primary plate-boundary structures are a series of strike-slip fault segments associated with pressure ridges, restraining bends, step overs and dogleg offsets indicating very active tectonics. Several distinct segments 50–100 km long cut across pre-existing structures inherited from former tectonic regimes or bypass recent morphologies formed under the current strike-slip regime. Along the most recent trace of the SOFZ, we measured a strike-slip offset of 16.5 km, which indicates steady activity for the past ~1.8 Ma if its current GPS-derived motion of 9.8 ± 2 mm a−1 has remained stable during the entire Quaternary.

During the Fanindien 2006 cruise of R/V 'Beautemps-Beaupre', high resolution multibeam bathymetry, sub-bottom profiling and sediment coring was carried out along the East African margin, offshore Tanzania and Mozambique (Indian Ocean). The newly acquired data reveal the presence of a giant deep-sea valley (the Tanzania channel) that is more than 10 km wide at 4000 m water depth, along the continental rise. The valley remains similar to 70 m deep and 7 km wide at 800 km from the Tanzania coast. Morphological comparison with worldwide submarine channels show that the Tanzania channel is one of the largest known submarine valleys. This discovery brings new light on development of submarine valleys that drain sediments originated from the East African Rift System (EARS) highlands (i.e. the Tanzania channel and its neighbor Zambezi channel located similar to 1000 km southward). Both of the systems have a morphology markedly different to the classical sinuous, V-shaped channels located at similar latitudes (e.g. the Zaire or Amazon channels). Their submarine drainage system consists of a downslope converging tributary canyons joining a central trunk channel in the continental rise. The presence of such giant deep-sea drainage systems is probably linked to a strong structural control on the sediment pathway, associated to a massive sediment transfer towards the Indian Ocean in relation with the tectonic activity of the East African Rift System (i.e. the uplift periods trough mid-Miocene and Plio-Pleistocene times) and its interplay with the East African equatorial climate changes.

This paper discusses the geodynamic evolution of the Makran accretionary prism from a new field investigation in the Pakistani area and from the interpretation of reprocessed seismic lines in the offshore area. The field reconnaissance has provided new structural data about the general structure of the prism and a rejuvenated stratigraphic chart based on new datings. This work outlines that the sediment input in the Makran originated from various origins during Cenozoic times: (1) direct influx from the Indus River conveying eroded series from the Indian shield or Himalayas, (2) strong erosion of the growing inner prism. En-echelon elongated anticlines which are cross-cut by strike-slip faults developed along the eastern Makran Range. Recent out-of-sequence thrust propagation has been evidenced in the onshore area in relation to recent erosion. A large un-deformed platform responsible for a huge trap for sedimentation developed during Miocene and Pliocene times between the emerged part of the Makran and the offshore active compressive front. The internal architecture of the prism is also strongly influenced by the propagation of the deformation with in secondary decollement levels. These upper detachments are hosted with in the Miocene slope-to-basin prograding wedges, upon which a recent normal growth fault system developed in the near offshore area, at the same time when compression occurred at the front of the prism.

The Makran accretionary prism developed in the north-western part of the Indian Ocean as a consequence of the subduction of the Arabian Sea since Late Cretaceous times. It extends from southern Iran to the Baluchistan region of Pakistan where it joins the Chaman-Ornach-Nal left-lateral strike-slip fault systems to the north and the Owen Fracture Zone-Murray Ridge transtensional (right-lateral) system to the south in a complex triple junction near the city of Karachi. In September to October of 2004, we surveyed most of the accretionary complex off Pakistan with R/V Marion Dufresne. We achieved a nearly continuous bathymetric mapping of the prism and the subduction trench from 62°30′E to the triple junction near 62°30′E together with nearly 1000 km of seismic reflection (13 lines) and we took 18 piston cores in different geological settings. One of the main results is that the frontal part of the Makran accretionary prism is less two-dimensional than previously expected. We interpret the along-strike tectonic variation as a consequence of lateral variations in sediment deposition as well as a consequence of the under-thrusting of a series of basement highs and finally of the vicinity to the triple junction.

Haiti is located on the western part of the island of Hispaniola, shared with the Dominican Republic in the east. Haiti is situated within the northern Caribbean plate boundary region where relative motion between the Caribbean and North American plates is accommodated by a complex system of fault-bounded microplates and tectonic blocks. Two seismogenic strike-slip faults related to this system are found in Haiti; the Enriquillo – Plantain Garden Fault Zone (EGPFZ) onshore southern Haiti, and the Septentrional Fault Zone (SFZ) offshore northern Haiti, with the southwest-verging, forward-propagating Haitian Fold-and-Thrust Belt situated in between them. The geology and geodynamic setting of Haiti became the focus of increased scientific interest following the January 12th 2010 Mw 7.0 Leogâne earthquake, which struck southern Haiti close to its capital Port-au-Prince. This study, which is a collaboration between Sorbonne Université, IFP Energies nouvelles (IFPEn), Université d’Etat d’Haïti (UEH), URGéo, and Bureau des Mines et de l’Energie d’Haïti (BME), is dedicated to increase our knowledge of the onshore geology of southern Haiti. There are three main objectives to this study; 1) identify the number and timing of deformation phases on the Southern Peninsula of Haiti, their regional impact, and the associated structural style of deformation and paleo-stress evolution, 2) constrain the deformation history of the southernmost onshore part of the Haitian Fold-and-Thrust Belt (the Chaîne des Matheux), the structural style of deformation and the associated paleo-stress evolution, and 3) characterize the interaction between fluids and deformation by examining the paleo-fluid circulation related to deformation in both regions. To fulfill these objectives this study integrates geological data and observations onshore Haiti from field campaigns in 2015 and 2017. Stratigraphic and structural data are combined with satellite imagery and digital elevation models to create four small-scale (~1:50.000) geological maps and associated cross sections. These are used to better understand and constraining the style of deformation in the region. Samples of host rocks and veins from fault zones and fractures are analyzed using a suite of analytical techniques, which include optical and cathodoluminescence microscopy, fluid inclusion microthermometry and Raman spectroscopy on fluid inclusions, x-ray diffraction, stable oxygen and carbon isotope geochemistry, and whole-rock geochemistry, all of which are integrated to constrain the paleofluid circulation. The results of this study indicate that 1) the Southern Peninsula evolved by basement-involved inversion, thrusting, and strike-slip, while 2) the style of deformation in the Chaîne des Matheux is predominantly thin-skinned controlled by shallow dipping decollement levels, although a component of thick-skinned basement-involved deformation is probable. The polyphase deformation history of the Southern Peninsula is characterized by three major tectonic events; 1) Deformation and uplift during the Maastrichtian and early Paleocene, 2) early Miocene compression and uplift that mainly affected the southwestern part of the Southern Peninsula, and 3) transpressive deformation from the late Miocene to recent. This last phase is characterized by a progressive focus of strike-slip activity along the EPGFZ, which accommodated a maximum of 15 km of left-lateral displacement since the late Messinian [...], Haïti est située sur la partie occidentale de l'île d'Hispaniola, qu'il partage avec la République dominicaine à l'est. Haïti est située en limite septentrionale des Caraïbes, où le mouvement relatif entre les plaques Caraïbes et Amérique du Nord est accommodé par un système complexe de microplaques de failles et de blocs tectoniques. Deux failles décrochantes sismogènes liées à ce système se trouvent en Haïti ; la zone de faille d'Enriquillo – Plantain Garden (EGPFZ) sur la partie sud d'Haïti et la zone de faille Septentrionale (SFZ) au large de la partie nord d'Haïti, tandis que la chaîne trans-haïtienne, composée de chevauchements d’unités tectoniques haïtiennes se propage vers le sud-ouest. La géologie et le contexte géodynamique d'Haïti font l'objet d'un regain d'intérêt scientifique à cause du séisme très destructeur de Mw 7.0, survenu le 12 janvier 2010, qui s’est produit au sud d'Haïti à Leogâne, près de la capitale Port-au-Prince. Cette étude, qui est une collaboration entre Sorbonne Université, IFP Energies nouvelles (IFPEn), l’Université d’Etat d’Haïti (UEH), URGéo, et le Bureau des Mines et de l’Energie d’Haïti (BME), participe à l'accroissement des connaissances géologiques de la zone méridionale d'Haïti. Elle comporte trois objectifs principaux ; 1) identifier le nombre et la chronologie des phases de déformation de la péninsule sud d'Haïti, leur impact régional, leur style structural, et l'évolution des paléo-contraintes, 2) contraindre l'histoire de la déformation de la zone frontale de la chaîne trans-haïtienne (la chaîne des Matheux), et (3) caractériser l'interaction entre les fluides et la déformation en examinant la circulation des paléo‐fluides associée à la déformation dans les deux régions. Pour atteindre ces objectifs, cette étude intègre des données géologiques et des observations à terre sur Haïti acquises lors de deux campagnes de terrain en 2015 et 2017. Les données stratigraphiques et structurales sont combinées avec l’étude des images satellitaires pour établir quatre cartes géologiques à petite échelle (~1:50.000) et des coupes transversales, qui permettent de mieux comprendre et de contraindre la déformation dans la région. Des échantillons de roches et de veines sont analysés à l'aide d'une série de techniques analytiques, incluant la microscopie optique, la cathodoluminescence, la micro‐thermométrie des inclusions fluides et la spectroscopie Raman sur ces inclusions, la diffraction des rayons X, la géochimie des isotopes stables, et la géochimie sur roche totale. L'ensemble des analyses est intégré afin de documenter et comprendre la circulation des paléo‐fluides. Les résultats de cette étude indiquent que la Péninsule du Sud s’est développée sur une large zone d’inversion bordée par des chevauchements impliquant le socle, tandis que la déformation dans la Chaîne des Matheux est principalement à l’origine d'une tectonique contrôlée par des niveaux de décollement peu profonds, suivie tardivement par des inversions de socle. L'histoire de déformation de la Péninsule du Sud est polyphasée et caractérisée par trois phases tectoniques majeures; 1) Compression et soulèvement durant le Maastrichtien et le Paléocène inférieur, 2) compression et soulèvement du Miocène inférieur qui affectaient principalement la partie sud‐ ouest de la Péninsule du Sud, et 3) déformation transpressive du Miocène supérieur à l’actuel. Cette dernière phase est caractérisée par une concentration progressive d'activité décrochante le long de l'EPGFZ, qui enregistre un maximum de 15 km de déplacement sénestre depuis la fin du Messinien [...]