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Article Dans Une Revue Geochemistry, Geophysics, Geosystems Année : 2017

Forearc seafloor unconformities and geology: insight from 3D seismic geomorphology analysis, Peru

Résumé

New 3D seismic data collected over 4870 km2 in the 3°45'–12°30'S Peruvian segment of the East Pacific subduction system image seafloor erosional surfaces that can be mapped across the forearc basins. Forearc basins experience various stresses, from their base where basal tectonic erosion acts to the seafloor which is influenced by aerial, shallow and deep water currents driven by waves or thermohaline oceanic currents. Previously there has been little interest in stresses on the upper layer and there is a lack of documentation of unconformities and the erosive processes in certain bathymetric domains in forearc basins. We address this with the study of examples sourced from 3D seismic reflection surveys of the seafloor offshore Peru. Unconformities occur in two distinctive bathymetric domains associated with the continental shelf and the upper slope of the margin. Identification and characterization of unconformity surfaces yield estimates of the amount of erosion at the modern seafloor that range from 18 to 100%. Regional physical oceanography allows us to calibrate potential candidates for these two distinctive domains. The first control on erosion is the dynamics of deep to intermediate oceanic currents related to the Humboldt-Peru Chile water masses, while the second is wave action in the shallower erosional surfaces. This study illustrates the unseen landscape of the forearc basins of South America and helps to highlight the importance of erosive surficial processes in subduction landscapes.
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Dates et versions

hal-01569621 , version 1 (27-07-2017)

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Domaine public

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Gérôme Calvès, Constance Auguy, Léopold de Lavaissière, Stéphane Brusset, Ysabel Calderon, et al.. Forearc seafloor unconformities and geology: insight from 3D seismic geomorphology analysis, Peru. Geochemistry, Geophysics, Geosystems, 2017, ⟨10.1002/2017GC007036⟩. ⟨hal-01569621⟩
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