Jacques Bourgois | Sorbonne Université, Université Pierre et Marie Curie & CNRS (original) (raw)

Papers by Jacques Bourgois

Pure and Applied Geophysics, 2016

This paper aggregates the main basic data acquired along the Chile Triple Junction (CTJ) area (45... more This paper aggregates the main basic data acquired along the Chile Triple Junction (CTJ) area (45!–48!S), where an active spreading center is presently subducting beneath the Andean continental margin. Updated sea-floor kinematics associated with a comprehensive review of geologic, geochemical, and geophysical data provide new constraints on the geodynamics of this puzzling area. We discuss: (1) the emplacement mode for the PleistoceneTaitao Ridge and the Pliocene Taitao Peninsula ophiolite bodies. (2) The occurrence of these ophiolitic complexes in association
with five adakite-like plutonic and volcanic centers of similar ages at the same restricted locations. (3) The inferences from the cooccurrence of these sub-coeval rocks originating from the same subducting oceanic lithosphere evolving through drastically different temperature–pressure (P–T) path: low-grade greenschist facies overprint and amphibolite-eclogite transition, respectively. (4) The evidences that document ridge-jump events and associated microplate individualization during subduction of the SCR1 and
SCR-1 segments: the Chonos and Cabo Elena microplates, respectively. The ridge-jump process associated with the occurrence of several closely spaced transform faults entering subduction is controlling slab fragmentation, ophiolite emplacement, and adakite-like production and location in the CTJ area. Kinematic inconsistencies in the development of the Patagonia slab
window document an 11- km westward jump for the SCR-1 spreading segment at*6.5-to-6.8 Ma. The SCR-1 spreading center is relocated beneath the North Patagonia Icefield (NPI). We arguethat the deep-seated difference in the dynamically sustained origin of the high reliefs of the North and South Patagonia Icefield (NPI and SPI) is asthenospheric convection and slab melting, respectively. The Chile Triple Junction area provides the basic constraints to define the basic signatures for spreading-ridge subduction
beneath an Andean-type margin.

Earth-Science Reviews, 2021

New fieldwork and tectonic analysis has been carried out along the Andean morphotectonic frontlin... more New fieldwork and tectonic analysis has been carried out along the Andean morphotectonic frontline between 46◦30’ and 47◦30′ S. The right lateral transtensional Marques–Zeballos Pass fault system (MZPRS) controlled the
800–1200 m uplift of the Andes at 16.1–18.1 Ma. Our data and analysis indicate that there was no lower Miocene contractile event along the Andean morphotectonic frontline. The Main Andean Thrust (MAT), which is deeply
rooted in the upper crust is a retroarc thrust dipping 10–15◦ westward, and provides evidence for major crustal shortening at ~120 Ma. At that time the arc volcanic strata of the Iba˜nez Fm (148–178 Ma) was transported eastward above the rift volcanic Quemado Fm (144179 Ma), which lies unconformably on the Deseado basement massif.
The geologic records from the fieldwork together with the available data allow us to identify the processes controlling the dynamic evolution of the two main topographic features of the studied Andean segment. (1) Upward convection originating from the subducted South Chile Ridge —1 segment (SCR —1) is dynamically sustaining the high topography of the North Patagonian Icefield (4070 m at the Mt. San Valentin, ~2 km higher
than the Southern South Volcanic Zone). This, together with the locus of maximum moisture being at 47◦S during glacial events has resulted in producing the two largest glacial lobes of Patagonia. (2) The 180 km long, E–W trending antiformal arch structure of the Mt. Zeballos Ridge (MZR, a hinge zone trending N–S along the MZPRS) straddling the Andes and the Foreland is proposed to be the morphological “twin” of the South American Plate Moho Plateau (SAM MOHO P). The SAM MOHO P controls the location of both the MZPRS and the MZR boundaries location through time. The Patagonia Slab Window and SAM asthenospheric dynamics (upward and
corner flows, respectively) and their in–depth interaction appear to control the morphotectonic evolution of the whole studied segment through a powerful feedback loop between tectonics, morphology, and climate, at least
for the past 3–4 Myr.

International Journal of Geosciences, 2024

The “mainstream” climatology (MSC)—i.e. which includes the Intergovernmental Panel on Climate Cha... more The “mainstream” climatology (MSC)—i.e. which includes the Intergovernmental
Panel on Climate Change (IPCC) community—considers the present
day massive release of greenhouse gases into the atmosphere as the main cause
of the current global warming trend. The main inference from this stance is
that the increase in temperature must occur after the release of greenhouse
gases originating from the anthropic activities. However, no scientific evidence
has been provided for this basic notion. Earth paleoclimatic records
document the antecedence of temperature over CO2 levels. For the past 65
Ma, the temperature parameter has controlled the subsequent increase in
CO2. This includes the three rapid aberrant shifts and extreme climate transients
at 55 Ma, 34 Ma, and 23 Ma [1]. The simple fact of their existence
points to the potential for highly nonlinear responses in climate forcing.
Whatever these shifts and transients are, CO2 remains a second order parameter
in their evolution through time. Confronted with the past, a suitable
response must therefore be given to the unresolved question of whether the
CO2 trends precede the temperature trends in the current period, or not. The
assertion that the current global warming is anthropogenic in origin implicitly
presupposes a change of paradigm, with the consequence (the increase in
CO2 levels) that occurred in Earth’s past being positioned as the cause of the
warming for its present day climatic evolution. The compulsory assumption
regarding the antecedence of CO2 levels over the temperature trends is associated
with the haziness of the methodological framework—i.e. the paradigm—
and tightens the research fields on the likely origins of global warming.
The possible involvement of an “aberrant” natural event, hidden behind
the massive release of greenhouse gases, has not been considered by the MSC.

Pure and Applied Geophysics, 2016

This paper aggregates the main basic data acquired along the Chile Triple Junction (CTJ) area (45... more This paper aggregates the main basic data acquired along the Chile Triple Junction (CTJ) area (45°-48°S), where an active spreading center is presently subducting beneath the Andean continental margin. Updated sea-floor kinematics associated with a comprehensive review of geologic, geochemical, and geophysical data provide new constraints on the geodynamics of this puzzling area. We discuss: (1) the emplacement mode for the Pleistocene Taitao Ridge and the Pliocene Taitao Peninsula ophiolite bodies. (2) The occurrence of these ophiolitic complexes in association with five adakite-like plutonic and volcanic centers of similar ages at the same restricted locations. (3) The inferences from the cooccurrence of these sub-coeval rocks originating from the same subducting oceanic lithosphere evolving through drastically different temperature-pressure (P-T) path: low-grade greenschist facies overprint and amphibolite-eclogite transition, respectively. (4) The evidences that document ridge-jump events and associated microplate individualization during subduction of the SCR1 and SCR-1 segments: the Chonos and Cabo Elena microplates, respectively. The ridge-jump process associated with the occurrence of several closely spaced transform faults entering subduction is controlling slab fragmentation, ophiolite emplacement, and adakite-like production and location in the CTJ area. Kinematic inconsistencies in the development of the Patagonia slab window document an 11-km westward jump for the SCR-1 spreading segment at *6.5-to-6.8 Ma. The SCR-1 spreading center is relocated beneath the North Patagonia Icefield (NPI). We argue that the deep-seated difference in the dynamically sustained origin of the high reliefs of the North and South Patagonia Icefield (NPI and SPI) is asthenospheric convection and slab melting, respectively. The Chile Triple Junction area provides the basic constraints to define the basic signatures for spreading-ridge subduction beneath an Andean-type margin.

Journal of Geophysical Research, 2007

This paper presents a combined analysis of geological and geophysical data collected both onshore... more This paper presents a combined analysis of geological and geophysical data collected both onshore and offshore along the northwestern Peru forearc area (3300–7300S), 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 modifying the uplifted coastal landforms along the coastal plain. Breaking-wave morphologic markers were dated using the in situ produced 10Be cosmonuclide. The data document a tectonic segmentation, allowing us to differentiate two areas with regard to their evolution through time: the northern Cabo Blanco and the southern Paita-Illesca segments. For the past 200 kyr, both segments uplifted at high rates of 10 to 20 mm yr1 through tectonic pulses coeval with the eustatic deglacial sea level rises of isotope stage 1 and warm isotope
substage 5e, respectively. The uplift and related extensive emersion of the coastal plain require high coupling along the subduction zone and/or underplating at depth. Offshore, industry-acquired reflection seismic lines combined with EM12 bathymetric data allow us to investigate the tectonic regime and deformation of the continental margin and shelf. Major dipping seaward detachments control the long-term subsidence of this area. These
main tectonic features define a tectonic segmentation. The Talara, Paita, and Sechura segments are identified from north to south. No clear tectonic correlation in time exists between the onshore and the continental margin segmentations, or in space either. The longterm subsidence of the offshore, indicative of subduction erosion working at depth, requires low coupling along the subduction channel at depth. The distribution of permanent
deformation along the northern Peru forearc area includes long-term uplift along the coastal plain and long-term subsidence along the continental margin, the neutral line being located within the 10 km seaward from the Present coastline. An extensive sequence of raised marine cliffs and associated notches evidences that the most recent uplift step (20–23 ka to
Present) along the Cabo Blanco segment is related to a sequence of major earthquakes. We infer that eustacy exerts important feedback coupling to the seismogenic behavior of the North Peru subduction zone. We speculate that during sea level fall, pore fluid pressure diminishes along the subduction channel inducing a possible seaward migration of the locked zone (i.e., migration of the updip limit) reaching a maximum by the end of the eustatic low stand. During eustatic sea level rise, pore fluid pressure increases along
the subduction channel. This in turn is capable of weakening the previously locked zone along the plate interface beginning an earthquake sequence. Earth’s orbital variations are a potential external cause that may control the physical processes at work along plate interface.

Geology, 1993

Tectonic history of the northern Peru convergent margin during the past 400 ka Geology on 4 June ... more Tectonic history of the northern Peru convergent margin during the past 400 ka Geology on 4 June 2009 geology.gsapubs.org Downloaded from E-mail alerting services cite this article to receive free e-mail alerts when new articles www.gsapubs.org/cgi/alerts click Subscribe to subscribe to Geology www.gsapubs.org/subscriptions/index.ac.dtl click Permission request to contact GSA http://www.geosociety.org/pubs/copyrt.htm#gsa click Opinions presented in this publication do not reflect official positions of the Society. positions by scientists worldwide, regardless of their race, citizenship, gender, religion, or political viewpoint. article's full citation. GSA provides this and other forums for the presentation of diverse opinions and articles on their own or their organization's Web site providing the posting includes a reference to the science. This file may not be posted to any Web site, but authors may post the abstracts only of their unlimited copies of items in GSA's journals for noncommercial use in classrooms to further education and use a single figure, a single table, and/or a brief paragraph of text in subsequent works and to make to employment. Individual scientists are hereby granted permission, without fees or further requests to GSA,

International journal of geosciences, 2024

Earth-Science Reviews, 2021

New fieldwork and tectonic analysis has been carried out along the Andean morphotectonic frontlin... more New fieldwork and tectonic analysis has been carried out along the Andean morphotectonic frontline between 46 • 30' and 47 • 30 ′ S. The right lateral transtensional Marques-Zeballos Pass fault system (MZPRS) controlled the 800-1200 m uplift of the Andes at 16.1-18.1 Ma. Our data and analysis indicate that there was no lower Miocene contractile event along the Andean morphotectonic frontline. The Main Andean Thrust (MAT), which is deeply rooted in the upper crust is a retroarc thrust dipping 10-15 • westward, and provides evidence for major crustal shortening at ~120 Ma. At that time the arc volcanic strata of the Ibañez Fm (148-178 Ma) was transported eastward above the rift volcanic Quemado Fm (144179 Ma), which lies unconformably on the Deseado basement massif. The geologic records from the fieldwork together with the available data allow us to identify the processes controlling the dynamic evolution of the two main topographic features of the studied Andean segment. (1) Upward convection originating from the subducted South Chile Ridge − 1 segment (SCR − 1) is dynamically sustaining the high topography of the North Patagonian Icefield (4070 m at the Mt. San Valentin, ~2 km higher than the Southern South Volcanic Zone). This, together with the locus of maximum moisture being at 47 • S during glacial events has resulted in producing the two largest glacial lobes of Patagonia. (2) The 180 km long, E-W trending antiformal arch structure of the Mt. Zeballos Ridge (MZR, a hinge zone trending N-S along the MZPRS) straddling the Andes and the Foreland is proposed to be the morphological "twin" of the South American Plate Moho Plateau (SAM MOHO P). The SAM MOHO P controls the location of both the MZPRS and the MZR boundaries location through time. The Patagonia Slab Window and SAM asthenospheric dynamics (upward and corner flows, respectively) and their in-depth interaction appear to control the morphotectonic evolution of the whole studied segment through a powerful feedback loop between tectonics, morphology, and climate, at least for the past 3-4 Myr.

Earth and Planetary Science Letters, 2002

When combined with the Miocene^Recent volcanic record of Baja California, a parallel drawn betwee... more When combined with the Miocene^Recent volcanic record of Baja California, a parallel drawn between the Chile and Mexico triple junction areas substantiates slab window development beneath northwestern Mexico during the past 12^10 Myr. The slab-free zone manifestations challenge the notion that ridge subduction has not occurred beneath the southern Baja California peninsula. The geochemically distinctive rocks from the Santa Clara volcanic field of west^central Baja California, including coeval adakites and niobium-enriched basalt, are commonly inferred to signal partial melting of the subducting plate at shallow depths and relatively high temperatures, before slab dehydration occurs. Such PT conditions for slab melting have only been observed in association with spreading-ridge subduction. We propose that slab window development beneath southern Baja California and mainland Mexico (30 ‡ to 18 ‡N) resulted from subduction of the East Pacific rise.

Geology, 1996

Chile margin triple junction area) Subduction erosion related to spreading-ridge subduction: Tait... more Chile margin triple junction area) Subduction erosion related to spreading-ridge subduction: Taitao peninsula Geology on 4 June 2009 geology.gsapubs.org Downloaded from E-mail alerting services cite this article to receive free e-mail alerts when new articles www.gsapubs.org/cgi/alerts click Subscribe to subscribe to Geology www.gsapubs.org/subscriptions/index.ac.dtl click Permission request to contact GSA http://www.geosociety.org/pubs/copyrt.htm#gsa click viewpoint. Opinions presented in this publication do not reflect official positions of the Society. positions by scientists worldwide, regardless of their race, citizenship, gender, religion, or political article's full citation. GSA provides this and other forums for the presentation of diverse opinions and articles on their own or their organization's Web site providing the posting includes a reference to the science. This file may not be posted to any Web site, but authors may post the abstracts only of their unlimited copies of items in GSA's journals for noncommercial use in classrooms to further education and to use a single figure, a single table, and/or a brief paragraph of text in subsequent works and to make GSA, employment. Individual scientists are hereby granted permission, without fees or further requests to

Tectonophysics, 1987

The Western Cordillera of Colombia was formed by intense alpine-type nappe-forming folding and th... more The Western Cordillera of Colombia was formed by intense alpine-type nappe-forming folding and thrusting. The Cretaceous (80-120 Ma B.P.) tholeiitic material of the Western Cordilleran nappes has been obducted onto the Paleozoic and Precambrian polymetamorphic micaschists and gneiss of the Central Cordillera. Near Yarumal, the Antioquia batholith (60-80 Ma B.P.) intrudes both obducted Cretaceous oceanic material and the polymetamorphic basement rock of the Central Cordillera. Therefore, nappe emplacement and obduction onto the Central Cordillera occurred during Late Senonian to Early Paleocene.
The nappes travelled from northwest to southeast so that the highest unit, the Rio Calima nappe therefore has the most northwestern source, whereas the lowest units originated from a more southeastward direction. Sedimentological analysis of the volcanoclastic and sandy turbidite material from each unit suggests a marginal marine environment. During Cretaceous times the opening of this marginal sea, from now on called the “Colombia marginal basin”, probably originated by detachment of a block from the South American continent related to the Farallon-South America plate convergence.
In the Popayan area (southern Colombia), the Central Cordilleran basement exhibits glaucophane schist facies metamorphism. This high pressure low temperature metamorphism is of Early Cretaceous (125 Ma B.P.) age and is
related to an undated metaophiohtic complex. The ophiolitic material originating from the Western Cordilleran is thrust over both the blueschist belt and the metaophiolitic complex. These data suggest that the “Occidente
Colombiano” suffered at least two phases of ophiolitic obduction during Mesozoic time.

HAL (Le Centre pour la Communication Scientifique Directe), Sep 16, 2002

International audienc

Comptes rendus de l'Académie des sciences. Série 2. Sciences de la terre et des planètes, Jun 1, 1998

Bulletin De La Societe Geologique De France, 1985

Bulletin de la Société Géologique de France, 1970

Stratigraphic and structural unit, flysch, Cretaceous, overthrust, Mollusca and foraminifera

Journal of African Earth Sciences (and the Middle East), 1993

Journal of Geophysical Research: Solid Earth, 1990

The Mendana Fracture Zone and the Trujillo Trough are two major intra‐oceanic features on the Naz... more The Mendana Fracture Zone and the Trujillo Trough are two major intra‐oceanic features on the Nazca Plate off Peru. During the SEAPERC cruise of the R/V Jean Charcot in 1986 (Jacques Bourgois,Chief Scientist), Sea Beam bathymetric data, single‐channel seismic records, geomagnetic and gravity measurements, and heat flow data have been obtained over these two areas. In this paper, we confirm that the Mendana Fracture Zone is actively opening perpendicular to its trend, resulting in the formation of new oceanic crust since about 3.5 Ma. We calculate that this new rift is propagating westward along the fracture zone at a velocity of about 10 cm yr−1 (or 2 cm yr−1 with respect to the trench). This extensional feature appears to be genetically linked with the Trujillo Trough, located 200 km to the north. This trough is bounded to the east by a left: lateral transpressive fault which became active probably at the time when the Mendana Rift started. We then discuss a possible mechanism to explain the origin of these two areas of intraoceanic deformation.

Earth-Science Reviews, 2021

New fieldwork and tectonic analysis has been carried out along the Andean morphotectonic frontlin... more New fieldwork and tectonic analysis has been carried out along the Andean morphotectonic frontline between 46 • 30' and 47 • 30 ′ S. The right lateral transtensional Marques-Zeballos Pass fault system (MZPRS) controlled the 800-1200 m uplift of the Andes at 16.1-18.1 Ma. Our data and analysis indicate that there was no lower Miocene contractile event along the Andean morphotectonic frontline. The Main Andean Thrust (MAT), which is deeply rooted in the upper crust is a retroarc thrust dipping 10-15 • westward, and provides evidence for major crustal shortening at ~120 Ma. At that time the arc volcanic strata of the Ibañez Fm (148-178 Ma) was transported eastward above the rift volcanic Quemado Fm (144179 Ma), which lies unconformably on the Deseado basement massif. The geologic records from the fieldwork together with the available data allow us to identify the processes controlling the dynamic evolution of the two main topographic features of the studied Andean segment. (1) Upward convection originating from the subducted South Chile Ridge − 1 segment (SCR − 1) is dynamically sustaining the high topography of the North Patagonian Icefield (4070 m at the Mt. San Valentin, ~2 km higher than the Southern South Volcanic Zone). This, together with the locus of maximum moisture being at 47 • S during glacial events has resulted in producing the two largest glacial lobes of Patagonia. (2) The 180 km long, E-W trending antiformal arch structure of the Mt. Zeballos Ridge (MZR, a hinge zone trending N-S along the MZPRS) straddling the Andes and the Foreland is proposed to be the morphological "twin" of the South American Plate Moho Plateau (SAM MOHO P). The SAM MOHO P controls the location of both the MZPRS and the MZR boundaries location through time. The Patagonia Slab Window and SAM asthenospheric dynamics (upward and corner flows, respectively) and their in-depth interaction appear to control the morphotectonic evolution of the whole studied segment through a powerful feedback loop between tectonics, morphology, and climate, at least for the past 3-4 Myr.

International Journal of Geosciences, 2024

The "mainstream" climatology (MSC)-i.e. which includes the Intergovernmental Panel on Climate Cha... more The "mainstream" climatology (MSC)-i.e. which includes the Intergovernmental Panel on Climate Change (IPCC) community-considers the present day massive release of greenhouse gases into the atmosphere as the main cause of the current global warming trend. The main inference from this stance is that the increase in temperature must occur after the release of greenhouse gases originating from the anthropic activities. However, no scientific evidence has been provided for this basic notion. Earth paleoclimatic records document the antecedence of temperature over CO 2 levels. For the past 65 Ma, the temperature parameter has controlled the subsequent increase in CO 2. This includes the three rapid aberrant shifts and extreme climate transients at 55 Ma, 34 Ma, and 23 Ma [1]. The simple fact of their existence points to the potential for highly nonlinear responses in climate forcing. Whatever these shifts and transients are, CO 2 remains a second order parameter in their evolution through time. Confronted with the past, a suitable response must therefore be given to the unresolved question of whether the CO 2 trends precede the temperature trends in the current period, or not. The assertion that the current global warming is anthropogenic in origin implicitly presupposes a change of paradigm, with the consequence (the increase in CO 2 levels) that occurred in Earth's past being positioned as the cause of the warming for its present day climatic evolution. The compulsory assumption regarding the antecedence of CO 2 levels over the temperature trends is associated with the haziness of the methodological framework-i.e. the paradigm-and tightens the research fields on the likely origins of global warming. The possible involvement of an "aberrant" natural event, hidden behind the massive release of greenhouse gases, has not been considered by the MSC.

Compte Rendus de l'Academie des Sciences (Paris), 1982

The age of the slope deposits are upper Oligocene to lower Miocene on the Leg 84 transect. Holes ... more The age of the slope deposits are upper Oligocene to lower Miocene on the Leg 84 transect. Holes 566, 567, 569, and 570 allowed us to identify an ophiolitic basement under these slope deposits. As on shore, this basement has an upper Campanian to Eocene sedimentary cover. The inner wall of the Middle America trench off Guatemala is not built with the Miocene accreting terranes of the oceanic Cocos plate which were drilled during Leg 67, but is an extension of the Middle America basement rock. Since the margin originated during upper Oligocene to lower Miocene the tectonic process is that of a normal faulting. The active margin off Guatemala shows a passive margin development; it is in a certain manner a C.E. margin (convergent extensive margin).

Pure and Applied Geophysics, 2016

Earth-Science Reviews, 2021

International Journal of Geosciences, 2024

Pure and Applied Geophysics, 2016

This paper aggregates the main basic data acquired along the Chile Triple Junction (CTJ) area (45... more This paper aggregates the main basic data acquired along the Chile Triple Junction (CTJ) area (45°-48°S), where an active spreading center is presently subducting beneath the Andean continental margin. Updated sea-floor kinematics associated with a comprehensive review of geologic, geochemical, and geophysical data provide new constraints on the geodynamics of this puzzling area. We discuss: (1) the emplacement mode for the Pleistocene Taitao Ridge and the Pliocene Taitao Peninsula ophiolite bodies. (2) The occurrence of these ophiolitic complexes in association with five adakite-like plutonic and volcanic centers of similar ages at the same restricted locations. (3) The inferences from the cooccurrence of these sub-coeval rocks originating from the same subducting oceanic lithosphere evolving through drastically different temperature-pressure (P-T) path: low-grade greenschist facies overprint and amphibolite-eclogite transition, respectively. (4) The evidences that document ridge-jump events and associated microplate individualization during subduction of the SCR1 and SCR-1 segments: the Chonos and Cabo Elena microplates, respectively. The ridge-jump process associated with the occurrence of several closely spaced transform faults entering subduction is controlling slab fragmentation, ophiolite emplacement, and adakite-like production and location in the CTJ area. Kinematic inconsistencies in the development of the Patagonia slab window document an 11-km westward jump for the SCR-1 spreading segment at *6.5-to-6.8 Ma. The SCR-1 spreading center is relocated beneath the North Patagonia Icefield (NPI). We argue that the deep-seated difference in the dynamically sustained origin of the high reliefs of the North and South Patagonia Icefield (NPI and SPI) is asthenospheric convection and slab melting, respectively. The Chile Triple Junction area provides the basic constraints to define the basic signatures for spreading-ridge subduction beneath an Andean-type margin.

Journal of Geophysical Research, 2007

Geology, 1993

International journal of geosciences, 2024

Earth-Science Reviews, 2021

New fieldwork and tectonic analysis has been carried out along the Andean morphotectonic frontlin... more New fieldwork and tectonic analysis has been carried out along the Andean morphotectonic frontline between 46 • 30' and 47 • 30 ′ S. The right lateral transtensional Marques-Zeballos Pass fault system (MZPRS) controlled the 800-1200 m uplift of the Andes at 16.1-18.1 Ma. Our data and analysis indicate that there was no lower Miocene contractile event along the Andean morphotectonic frontline. The Main Andean Thrust (MAT), which is deeply rooted in the upper crust is a retroarc thrust dipping 10-15 • westward, and provides evidence for major crustal shortening at ~120 Ma. At that time the arc volcanic strata of the Ibañez Fm (148-178 Ma) was transported eastward above the rift volcanic Quemado Fm (144179 Ma), which lies unconformably on the Deseado basement massif. The geologic records from the fieldwork together with the available data allow us to identify the processes controlling the dynamic evolution of the two main topographic features of the studied Andean segment. (1) Upward convection originating from the subducted South Chile Ridge − 1 segment (SCR − 1) is dynamically sustaining the high topography of the North Patagonian Icefield (4070 m at the Mt. San Valentin, ~2 km higher than the Southern South Volcanic Zone). This, together with the locus of maximum moisture being at 47 • S during glacial events has resulted in producing the two largest glacial lobes of Patagonia. (2) The 180 km long, E-W trending antiformal arch structure of the Mt. Zeballos Ridge (MZR, a hinge zone trending N-S along the MZPRS) straddling the Andes and the Foreland is proposed to be the morphological "twin" of the South American Plate Moho Plateau (SAM MOHO P). The SAM MOHO P controls the location of both the MZPRS and the MZR boundaries location through time. The Patagonia Slab Window and SAM asthenospheric dynamics (upward and corner flows, respectively) and their in-depth interaction appear to control the morphotectonic evolution of the whole studied segment through a powerful feedback loop between tectonics, morphology, and climate, at least for the past 3-4 Myr.

Earth and Planetary Science Letters, 2002

Geology, 1996

Tectonophysics, 1987

HAL (Le Centre pour la Communication Scientifique Directe), Sep 16, 2002

International audienc

Comptes rendus de l'Académie des sciences. Série 2. Sciences de la terre et des planètes, Jun 1, 1998

Bulletin De La Societe Geologique De France, 1985

Bulletin de la Société Géologique de France, 1970

Stratigraphic and structural unit, flysch, Cretaceous, overthrust, Mollusca and foraminifera

Journal of African Earth Sciences (and the Middle East), 1993

Journal of Geophysical Research: Solid Earth, 1990

Earth-Science Reviews, 2021

New fieldwork and tectonic analysis has been carried out along the Andean morphotectonic frontlin... more New fieldwork and tectonic analysis has been carried out along the Andean morphotectonic frontline between 46 • 30' and 47 • 30 ′ S. The right lateral transtensional Marques-Zeballos Pass fault system (MZPRS) controlled the 800-1200 m uplift of the Andes at 16.1-18.1 Ma. Our data and analysis indicate that there was no lower Miocene contractile event along the Andean morphotectonic frontline. The Main Andean Thrust (MAT), which is deeply rooted in the upper crust is a retroarc thrust dipping 10-15 • westward, and provides evidence for major crustal shortening at ~120 Ma. At that time the arc volcanic strata of the Ibañez Fm (148-178 Ma) was transported eastward above the rift volcanic Quemado Fm (144179 Ma), which lies unconformably on the Deseado basement massif. The geologic records from the fieldwork together with the available data allow us to identify the processes controlling the dynamic evolution of the two main topographic features of the studied Andean segment. (1) Upward convection originating from the subducted South Chile Ridge − 1 segment (SCR − 1) is dynamically sustaining the high topography of the North Patagonian Icefield (4070 m at the Mt. San Valentin, ~2 km higher than the Southern South Volcanic Zone). This, together with the locus of maximum moisture being at 47 • S during glacial events has resulted in producing the two largest glacial lobes of Patagonia. (2) The 180 km long, E-W trending antiformal arch structure of the Mt. Zeballos Ridge (MZR, a hinge zone trending N-S along the MZPRS) straddling the Andes and the Foreland is proposed to be the morphological "twin" of the South American Plate Moho Plateau (SAM MOHO P). The SAM MOHO P controls the location of both the MZPRS and the MZR boundaries location through time. The Patagonia Slab Window and SAM asthenospheric dynamics (upward and corner flows, respectively) and their in-depth interaction appear to control the morphotectonic evolution of the whole studied segment through a powerful feedback loop between tectonics, morphology, and climate, at least for the past 3-4 Myr.

International Journal of Geosciences, 2024

Compte Rendus de l'Academie des Sciences (Paris), 1982

Abstract The Beni Bousera peridotite massif and its metamorphic surrounding rocks have been analy... more Abstract The Beni Bousera peridotite massif and its metamorphic surrounding rocks have been analyzed by the fission track (FT) method. The aim was to determine the cooling and uplift history of these mantle and associated crustal rocks after the last major metamorphic event that dates back to the Lower Miocene–Upper Oligocene time (∼22–24 Ma). The zircon FT analyses give an average cooling—i.e., below 320 °C—age of ∼19.5 Ma. In addition, the apatite FT data give an average cooling—i.e., below 110 °C—age of ∼15.5 Ma. Taking into account the thermal properties of the different thermochronological systems used in this work, we have estimated a rate of cooling close to 50 °C/Ma. This cooling rate constrains a denudation rate of
about ∼2mmyear−1 from 20 to 15 Ma. These results are similar to those determined in the Ronda peridotite massif of the Betic Cordilleras documenting that some ultrabasic massifs of the internal zones of the two segments of the Gibraltar Arc have a similar evolution. However, Burdigalian sediments occur along the Betic segment (Alozaina area, western Betic segment)
unconformably overlying peridotite. At this site, ultramafic rock was exposed to weathering at ages ranging from 20.43 to 15.97 Ma. Since the Beni Bousera peridotite was still at depth until 15.5 Ma, we infer that no simple age projection from massif to massif is possible along the Gibraltar Arc. Moreover, the confined fission track lengths data reveal that a light warming (∼100 °C) has reheated the massif during the Late Miocene before the Pliocene–Quaternary tectonic uplift.

Nouvel Observateur, 1991

L'expédition Nautiperc (mars-avril, 1991) a permis d'effectuer une trentaine de plongées du subme... more L'expédition Nautiperc (mars-avril, 1991) a permis d'effectuer une trentaine de plongées du submersible Nautile dans la fosse du Pérou (6000 m). Pour en rendre compte auprès du grand public le chef de mission, Dr Jacques Bourgois (CNRS) avait invité à bord un journaliste du "Nouvel Observateur". Il en est résulté un article de 4 pages dans la revue grand public.

Dr Jacques Bourgois a invité à bord du Nadir un reporter du Nouvel Observateur, navire qui op