François Michaud

• Sorbonne University

We investigate the evolution of the onshore Manabí forearc basin in Ecuador, which has developed on accreted oceanic terranes. We use 2D seismic profiles to identify 10 seismic units, separated by 9 unconformities. These units were dated by correlation with Ricaurte-1 well and regional stratigraphy. Unit S1 represents the first depocenter developed...

The southern Ecuadorian forearc system is related to the subduction of the oceanic Farallon/Nazca Plate beneath the continental South American Plate since the Late Cretaceous, and currently evolves with the dynamic of a tectonic block called North Andean Sliver. To explore the structural architecture and processes controlling the Upper Cretaceous-C...

Identifying the sources of distal tephra in marine sediments or polar ice provides clues on the dynamic and large-scale impact of major volcanic eruptions. However, determination of the volcanic source of distal tephra is challenging due to size-dependent fractionation during atmospheric transport that modifies the mineral, chemical and even isotop...

The offshore Tumbes-Guayaquil forearc basin in the accretionary prism of Northern Peru-Southern Ecuador shows evidence of gravity-driven large-scale deformation systems active during the Late Neogene-Quaternary period. Subsurface data and the construction of eight structural cross-sections show that the ∼8 km-thick Oligocene-Quaternary sedimentary...

Tephra layers preserved in marine sediments are strong tools to study the frequency, magnitude and source of past major explosive eruptions. Thirty‐seven volcanoes from the Ecuadorian and Colombian arc, in the northern Andes, experienced at least one eruption during the Holocene. The volcanic hazard is therefore particularly high for the populated...

We investigate the relationship between the long‐term (Quaternary) interplate coupling and the short‐term geodetically derived interseismic coupling at the Central Ecuador subduction zone. At this nonaccretionary margin, the Cabo Pasado shelf promontory and coastal area are associated with two inter‐plate geodetically locked patches. The deepest pa...

A marine sediment core located off the southernmost part of the Baja California Peninsula, NE Pacific, is analyzed to investigate a submarine mass failure. We examine the lithofacies and sedimentary structures, the total organic (TOC) and inorganic (TIC) carbon, the grain size composition, and the degree of fragmentation in foraminifera tests. The...

Extensional faults are often observed along subduction zones as a response of a margin collapse. However, their role remain underestimated within the structural evolution of forearc systems. In southern Ecuador, the oblique subduction of the Nazca Plate beneath South America led to the formation of the Cretaceous-Miocene NW-SE Chongón-Colonche Cord...

The name Apinella Granier et al., 1986, which was preoccupied by Apinella Rafinesque, 1840, a genus of Umbelliferae/Apiaceae, is replaced here by Apianella Granier & Michaud, nom. nov.

In this study, we provide the first detrital apatite (U–Th-Sm)/He (AHe) and zircon U–Pb ages to establish a detailed short-term chronology of the burial and exhumation history, which occurred in the Coastal Cordillera along the forearc domain of Ecuador. First, our results allowed us to define a range of maximum deposition ages for the Angostura Fo...

The active margin of Ecuador is characterized by strong tectonic erosion that contributes to the formation of a deep trench filled by a complex suite of sedimentary facies. Gravity flow sedimentation is ubiquitous along the margin and facies range from laterally continuous m-thick mass transport deposits to isolated cm-thick turbidites intercalated...

Ecuadorian Coastal Region represents an inner-shelf assemblage underlain by an allochthonous oceanic terrane accreted to the NW South American margin during the Upper Cretaceous. Basement rocks consist of an incomplete ophiolitic sequence composed of gabbro and basalt. Cenozoic infilling is arranged into local sedimentary basins (e.g. Progreso, Man...

Deciphering the migration pattern of the Esmeraldas submarine Canyon (EC) and its history of cut‐and‐fill allows constraining the Pliocene‐Pleistocene tectonic evolution of the Ecuador‐Colombia convergent margin. Swath bathymetry, multichannel seismic reflection, and chronological data show that the EC is a 143‐km‐long, shelf‐incising, river‐connec...

We characterise the aftershock sequence following the 2016 Mw=7.8 Pedernales earthquake. More than 10,000 events were detected and located, with magnitudes up to 6.9. Most of the aftershock seismicity results from interplate thrust faulting, but we also observe a few normal and strike-slip mechanisms. Seismicity extends for more than 300 km along s...

We characterise the aftershock sequence following the 2016 Mw=7.8 Pedernales earthquake. More than 10,000 events were detected and located, with magnitudes up to 6.9. Most of the aftershock seismicity results from interplate thrust faulting, but we also observe a few normal and strike-slip mechanisms. Seismicity extends for more than 300 km along s...

Forearc basins have developed along accretionary and nonaccretionary convergent margins. Here, we investigate the evolution of an offshore nonaccretionary-type forearc basin that has developed along the Ecuadorian convergent margin. We used 2D-Multichannel Seismic Reflection profiles to recognize five seismic units overlying the acoustic basement....

Based on swath bathymetry, two-dimensional, high-resolution seismic reflection profiles, and Ocean Drilling Program/Deep Sea Drilling Project (ODP/DSDP) data, we describe a seafloor honeycomb pattern and propose a model for its formation in Pliocene–Miocene carbonate deposited on the uneven oceanic basement of the Carnegie Ridge (offshore Ecuador)....

The longitudinal profile of a river channel can be described in function of mathematical expressions. The logarithmic fit is the most used method to describe the relative equilibrium of a channel elevation profile. Rivers showing zones of high channel gradient and convex-upward profiles can be evaluated in function of the offset distance with respe...

En los últimos años el interés por la zona marina y marino-costera se ha ampliado y profundizado, sin embargo, aún somos pocos quienes desarrollamos nuestra labor investigativa en el territorio marítimo ecuatoriano. Esta situación está cambiando, pero aún falta recorrer un largo camino para que la investigación marítima en nuestro país alcance el n...

With hull-mounted multibeam echosounder data, we report for the first time along the active Ecuadorian margin, acoustic signatures of water column fluid emissions and seep-related structures on the seafloor. In total 17 flare-shaped acoustic anomalies were detected from the upper slope (1250 m) to the shelf break (140 m). Nearly half of the flare-s...

The uplift of the coastal cordillera of central Ecuador is a likely consequence of the subduction of the Carnegie Ridge, a 400-km-long and 2-km-high topographic asperity. This study aims at analyzing the impact of the subduction of the Carnegie Ridge on the continental shelf sedimentation during the Quaternary. We interpret high-resolution (50–450...

With hull-mounted multibeam echosounder data, we report for the first time along the active Ecuadorian margin, acoustic signatures of water column fluid emissions and seep-related structures on the seafloor. In total 17 flare-shaped acoustic anomalies were detected from the upper slope (1250 m) to the shelf break (140 m). Nearly half of the flare-s...

— Au Jurassique et au Crétacé, le peuplement des plates-formes des marges atlantiques par les grands foraminifères benthi-ques s’est opéré d’Ouest en Est. Caractéristiques des zones tropicales ces organismes n’ont atteint la marge américaine de l’océan qu’au Callovien ou à l’Oxfordien. Jusqu’au Sénonien, les grands forammifères de cette marge étaie...

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...

Análisis morfológico, perfiles topográficos Perfiles de sísmica VHR (campaña Atacames 2012. Fuente: 6 mini GI guns 50-450 khz. Recepteur : flûte 72 traces de 6,25m) • Estratigrafía sísmica (identificación des facies y unidades) • Identificación de secuencias asociadas a las variaciones eustáticas • Edad de las unidades Resultados: Sísmica VHR Ident...

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 devel-opment and stratigraphic evolution of the margin based on the sismo-stratigraphic analysis o...

Les canyons sous-marins sont des incisions profondes de la plateforme et du talus continental des marges actives et passives qui constituent des axes majeurs de transfert de sédiment du continent vers les bassins océaniques profonds. La géométrie des canyons (forme et remplissage sédimentaire) est fortement contrôlée par les variations climatiques...

The propagation of the Pacific-Cocos Segment of the East Pacific Rise (EPR-PCS) has significantly altered the plate configuration at the north end of the Middle America Trench. This ridge propagation, the collision of the EPR-PCS with the Middle America Trench, the separation of the Rivera and Cocos plates and the formation of the Rivera Transform...

Three thousand kilometres of multichannel (MCS) and wide-angle seismic profiles, gravity and magnetic, multibeam bathymetry and backscatter data were recorded in the offshore area of the west coast of Mexico and the Gulf of California during the spring 1996 (CORTES survey). The seismic images obtained off Puerto Vallarta, Mexico, in the Jalisco sub...

Abstract—The study of the geochemical compositions and K-Ar or Ar-Ar ages of ca. 350 Neogene and Quaternary lavas from Baja California, the Gulf of California and Sonora allows us to discuss the nature of their mantle or crustal sources, the conditions of their melting and the tectonic regime prevailing during their genesis and emplacement. Nine pe...

To better define the morphotectonic elements and tectonic development of the Mid-Rivera-Transform Discordance, multibeam bathymetric, seafloor backscatter, multichannel seismic reflection and total field marine magnetic data were collected along the entire Rivera Transform west of 107°W during the BART and FAMEX campaigns of the N.O. L’Atalante con...

The relative motion of the Pacific plate with respect to the North America plate is partitioned between transcurrent faults located along the western margin of Baja California and transform faults and spreading ridges in the Gulf of California. However, the amount of right lateral offset along the Baja California western margin is still debated. We...

Introducción La formación Borbón (Bristow y Hoffsteter, 1977) fue definida como un depósito detrítico de extensión regional a lo largo de la cordillera costera de Ecuador. Tiene una edad según la bibliografía que va del Plioceno al Pleistoceno temprano (Benítez, 1995; Deniaud, 1998). Los afloramientos mejor expuestos están sobre el flanco oriental...

La Cordillera Costera del Ecuador (cuyo punto culminante se encuentra alrededor de 800 m) tiene una longitud de 600 kilómetros, constituyendo así una importante barrera de drenaje: ríos provenientes de los Andes son desviados tanto hacia el Río Guayas al Sur como al Río Esmeraldas al Norte. De esta manera surgen varias interrogantes: ¿De qué manera...

The relative motion of the Pacific plate with respect to the North America plate is partitioned between transcurrent faults located along the western margin of Baja California and transform faults and spreading ridges in the Gulf of California. However, the amount of right lateral offset along the Baja Cali-fornia western margin is still debated. W...

A compilation of swath bathymetric data from the Ecuador South-Colombia subduction zone allows a detailed characterization of the geomorphology of the trench and margin seafloor. These data are used together with seismic reflection profiles to evaluate the age and the effects of the Carnegie ridge (CR) subduction, and thus determine the modes of ma...

The coastal cordillera of Ecuador (culminating point around 800 m) includes on its littoral margins uplifted marine terraces (maximum known 360 m). The coastal cordillera constitutes an important barrier of drainage and on nearly 600 km the drainage resulting from the Andes is diverted towards Río Guayas in the South and Río Esmeraldas in North. Wh...

The discordance in the orientation of the eastern and western parts of the Rivera Transform is well established and a single Rivera-Pacific Euler vector has yet to be found which can adequately fit these two trends. As a result, it has been proposed that although the western part of the transform is indeed a transform boundary between two ridged pl...

The proposed ages for the collision of the Carnegie Ridge with the South America trench, offshore Ecuador, range from 1 to 15 Ma. In this time frame, many geological features of Ecuador are commonly linked to the subduction of the Carnegie Ridge. (1) After the ridge collided with the trench at ca. 15 Ma, the subsequent interplate coupling produced...

Resumen. La exploración de los océanos y de los márgenes continentales usando los métodos geofísicos marinos ha sido una de las claves en los avances de nuestra comprensión de la estructura interna de la Tierra axial como de los mecanismos de su evolución, y en particular de la tectónica de placas, en el último siglo. El enorme potencial de estos m...

To better understand the recent motion of the Pacific plate relative to the Rivera plate and to better define the limitations of the existing Rivera–Pacific plate motion models for accurately predicting this motion, total-field magnetic data, multibeam bathymetric data and sidescan sonar images were collected during the BART and FAMEX campaigns of...

The North Andean Block northward drifting has been related to lateral (opening of the Guayaquil Gulf) and vertical motions (tectonic inversion of the Loja, Catamayo, Gonzanamá and Malacatos - Vilcabamba basins, Fig.1). Hungerbühler et al. (2002) propose that the evolution of the sedimentary infill of these basins took place during two different sta...

Les données de bathymétrie haute résolution enregistrées sur les flancs de la ride de Carnegie (Equateur) pendant la campagne SALIERI (du N/O SONNE), montrent, entre 1 500 et 2700 m de profondeur, des zones parsemées de champs de dépressions circulaires fermées de plus de 300 m de profondeur et de 2 à 3 km de diamètre. Ces structures circulaires sp...

This work presents a combined analysis of data collected both onshore and offshore amlong the northwestern Peru forearc area (3°30’-7°30’S), from the coastal plain to the trench axis.

[1] This paper presents a combined analysis of geological and geophysical data collected both onshore and offshore along the northwestern Peru forearc area (3°30′–7°30′S), from the coastal plain to the trench axis. Onshore, geomorphic analysis places constraints on the relative importance of eustatic versus tectonic factors in preserving and modify...

Neogene magmatic activity in Central Baja California underwent a major change at ca. 12.5 Ma, when the Pacific–Farallon active oceanic ridge collided with the trench east of Vizcaíno Peninsula. The calc-alkaline magmatism which built the Comondú volcanic arc vanished and was replaced by unusual volcanic associations, which were erupted within six L...

A morphometric analysis of submarine landslides on the continental slope of north Colombia – south Ecuador convergent margin provides insights into hazards, including mass movements locations, size of failures and location control. Bathymetric and seismic data acquired in 2005 revealed three distinctive types of locations with the occurrence of pot...

At 12.5 Ma, after subduction below the North American plate stops, right-lateral transform motion occurs along the margin between the Pacific and North American plates. The Tosco-Abreojos fault zone, located along the western margin of southern Baja California, has been interpreted as the main transform boundary between both plates until early Plio...

Studies of hydrate occurrence have been very limited at the Mexican Pacific margins. Five seismic reflection profiles across the west margin of the Baja California Peninsula were examined to determine the temperature and pressure at sediment layers containing gas hydrate, inferred from the presence of BSR events. During March and April, 2002, a Fre...

To better constrain the Euler pole describing the recent motion of the Pacific plate relative to the Rivera plate, total- field magnetic data, multi-beam bathymetric data and sidescan sonar images were collected during the BART and FAMEX campaigns of the N/O L'Atalante conducted in April and May of 2002 in the area surrounding the Moctezuma Spreadi...

The Gulf of California (GC) is a right lateral transform fault zone developed as a series of short spreading segments that delineates the boundary between the Pacific and North American plates. From April to May 1996, over 1500 miles of seismic reflection data (3000 c.i. and shot rate of 30s), potential field, seabeam and backscattering have been a...

Interpretation of industrial multichannel seismic profiles and well data are used to identify the main tectonic features of the Gulf of Guayaquil (GG) area. These include two E-W trending major detachments: the Posorja and the Jambelı´ detachment systems, which represent half grabens with oppositely dipping detachments, to the south and to the nort...

Lake Chapala, located 120km northeast of Colima Volcano, lies at the north and northeast of the Citala rift in the Trans-Mexican Volcanic Belt. It belongs to the watershed of the Lerma River, which originates from the Mexico City area, 450km to the east. Sediment cores, 0.5–2m long, were collected from the lake. Magnetic susceptibility of the lake...

El movimiento hacia el norte del Bloque Norandino ha sido relacionado con movimientos laterales (apertura del Golfo de Guayaquil) y movimientos verticales (inversión tectónica de las cuencas de Cuenca, Loja, Catamayo, Gonzanamá y Malacatos – Vilcabamba). Hungerbühler et al. (2002) establecen una cronología detallada de las distintas formaciones pre...

The interaction of the Pacific-Farallon spreading centers with the North American convergent margin off Baja California, Mexico, supposedly ceased at 12 Ma, when plate convergence and seafloor spreading stopped. We propose a new geodynamic evolution based on full bathymetry coverage and magnetic profiles from 23°N to 27°N (Famex cruise of the R/V L...

The N-Ecuador and SW-Colombia margin underwent great (7.7

Ecuador and southwest (SW) Colombia suffered widespread damage during the twentieth century as a result of some of the greatest subduction earthquakes and associated tsunamis ever recorded. In 1906, the Ecuador-SW Columbia margin, located at the transition between the continent and deep ocean, ruptured over a 500-kilometer length as a single great...

Based on multichannel seismic reflection profiles and well data acquired by Petroecuador (Ecuadorian Petroleum Company) during the past two decades, we document the geodynamic evolution of the Golfo de Guayaquil (GG) area.

The direction of convergence between the Rivera and North American plates becomes progressively more oblique (in a counter-clockwise sense as measured relative to the trench-normal direction) northwestward along the Jalisco subduction zone. By analogy to other subduction zones, the forces resulting from this distribution of convergence directions a...

Offshore Ecuador, the Carnegie Ridge is a volcanic ridge with a carbonate sediment drape. During the SALIERI Cruise, multibeam bathymetry was collected across Carnegie Ridge with the Simrad EM120 of the R/V SONNE. The most conspicuous features discovered on the Carnegie Ridge are fields of circular closed depressions widely distributed along the mi...

The crustal structure of the northern Gulf of California transtensional margin has been investigated by a 280-km-long NW-SE profile, including deep multichannel seismic reflection and densely sampled refraction/wide-angle reflection seismic information combined with gravity modeling. The seismic and gravity modeling constrains two thinned crustal a...

Journal of Geophysical Research, v. 110, p. B01313, 2005. http://dx.doi.org/10.1029/2003JB002941

A los 12.5 Ma, después del cese de la subducción de la placa Guadalupe debajo de la placa América del Norte, el margen continental actuó como frontera transformante entre las placas Pacífi co y América del Norte. La zona de falla Tosco-Abreojos localizada a lo largo de dicho margen fue interpretada como el mejor candidato para acomodar este movimie...

The first proposal of an intra-transform spreading center along the Rivera transform at 108°15'W was based on microseismicity data. During projects BART and FAMEX, conducted during 2002 aboard the N/O L'Atalante, 100% of the Rivera transform was covered by multibeam bathymetric and seafloor reflectivity data. These data show that the Rivera transfo...

Subduction of the Nazca plate beneath the Ecuador-Colombia margin has produced four megathrust earthquakes during the last century. The 500-km-long rupture zone of the 1906 (Mw = 8.8) event was partially reactivated by three thrust events, in 1942 (Mw = 7.8), 1958 (Mw = 7.7), and 1979 (Mw = 8.2), whose rupture zones abut one another. Multichannel s...

Subduction of the Nazca plate beneath the Ecuador-Colombia margin has produced four megathrust earthquakes during the last century. The 500-km-long rupture zone of the 1906 (Mw = 8.8) event was partially reactivated by three thrust events, in 1942 (Mw = 7.8), 1958 (Mw = 7.7), and 1979 (Mw = 8.2), whose rupture zones abut one another. Multichannel s...

[1] During the FAMEX cruise of the R/V L’Atalante (April 2002), swath bathymetry and seismic profiles were recorded along the Baja California margin from 23� to 27�N. The upper-slope of the margin exhibits active faulting of recent sediments along the Tosco-Abreojos fault system (TAFS). Flower structures evidence strike-slip motion along the TAFS....

[1] During the FAMEX cruise of the R/V L'Atalante (April 2002), swath bathymetry and seismic profiles were recorded along the Baja California margin from 23° to 27°N. The upper-slope of the margin exhibits active faulting of recent sediments along the Tosco-Abreojos fault system (TAFS). Flower structures evidence strike-slip motion along the TAFS....

In April 2002, R/V L'Atalante collected swath-bathymetry data along with surface and deep-tow magnetic data in the oceanic basin adjacent to Baja California (FAMEX cruise). The new data evidence a series of short extinct spreading-ridge segments extending from the Clarion FZ to the Shirley FZ where it connects with the Guadalupe extinct ridge. This...

In April 2002, R/V L Atalante collected swath-bathymetry, surface and deep tow magnetic, gravity and seismic data in order to investigate the existence, characteristics and age of the Guadalupe and Magdalena fossil spreading centers that were postulated off Baja California (eastern Pacific Ocean). The new data confirm the existence of these extinct...