16 septembre 2008
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/2008
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BRIEF DESCRIPTION OF ONGOING ACADEMIC RESEARCH
Since about ten years, part of my studies focused at the interface of tectonics, oceanography, and climatology. The main objective is to understand the feedback processes between climate and tectonic deformation at the time scale of the glacial-interglacial cycle. Abrupt changes in the climate system induce tectonic responses including at the millennium time scale. To document these changes, to date them precisely and to understand the mechanisms require to use technique of analytical chemistry including 10Be cosmogenic isotopes.
Over the past ten years, my main contributions are related to the following topics:
(1) At the Chile triple junction area (Bourgois et al., 2000), the climate-induced variation of the sediment supply to the trench axis is the main factor controlling the continental margin tectonic regime. During the warm period of the interglacial episode at 117-130,000 years, rapid increase of the trench sediment accumulation caused the margin to switch from subduction-erosion or nonaccretion to subduction-accretion.
(2) Along the northwestern Peru forearc area (Bourgois et al., 2007), we infer that eustacy exerts important feedback coupling to seismic behavior of the Northern 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 reaching a maximum by the end of the eustatic low stand at 19-23,000 years.
(3) At the Chile triple junction area (Bourgois et al., in progress), the major retreat of the northern Patagonia ice cap at 11-14,000 years controls the tectonic rebound of this segment of the Andes, and the funneling of the Andean runoff to the Pacific.
(1) At the Chile triple junction area (Bourgois et al., 2000), the climate-induced variation of the sediment supply to the trench axis is the main factor controlling the continental margin tectonic regime. During the warm period of the interglacial episode at 117-130,000 years, rapid increase of the trench sediment accumulation caused the margin to switch from subduction-erosion or nonaccretion to subduction-accretion.
(2) Along the northwestern Peru forearc area (Bourgois et al., 2007), we infer that eustacy exerts important feedback coupling to seismic behavior of the Northern 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 reaching a maximum by the end of the eustatic low stand at 19-23,000 years.
(3) At the Chile triple junction area (Bourgois et al., in progress), the major retreat of the northern Patagonia ice cap at 11-14,000 years controls the tectonic rebound of this segment of the Andes, and the funneling of the Andean runoff to the Pacific.
Selected references
(56) Bourgois, J., Bigot-Cormier, F., Bourles, D., Braucher, R., Dauteuil, O., Witt, C., Michaud, F., northwestern Peru coastal plain, and continental slope during the past 200 kyr. Journal of Geophysical Research, 112, B04104, doi:10.1029/2006JB004491.
(42) Bourgois, J., Guivel, C., Lagabrielle, Y., Calmus, T., Boulègue, J., Daux, V., 2000 Glacial-interglacial trench supply variation, spreading-ridge subduction, and feedback controls on the Andean margin development at the Chile triple junction area (45-48° S), Journal of Geophysical Research, 105, 8355-8386.
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