Seabeam and seismic reflection imaging of the tectonic regime of the Andean continental margin off Peru (4°S to 10°S)

Bourgois, Jacques; Pautot, Guy; Bandy, William L.; Boinet, T.; Chotin, P.; Huchon, Philippe; Lépinay, Bernard Mercier de; Monge, F.; Monlau, J.; Pelletier, Bernard; Sosson, Marc; Huene, Roland von

doi:10.1016/0012-821x(88)90068-4

Cited by 34 publications

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“…The aim of this article is to describe the compilation of data from these two different techniques of multi-beam bathymetric surveys. As discussed below, the results show the occurrence of several kilometre-sized arcuate scarps related to several mega submarine slides instead of one single slide as proposed previously (Bourgois et al, 1988Von Huene et al, 1989). In order to discuss the different processes involved in such successive slope failures, a detailed analysis of the tectonic framework needs to be conducted first.…”

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AbstractA mega-submarine slide was evidenced along the Peruvian margin during a Seabeam survey of the R/V Charcot (Bourgois et al, 1986). The debris-slide was initially interpreted as the result of the slope failure occurring along a seaward curved scarp, and extending from east to west, along the line of maximum slope.

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“…They include landslides along the steep submerged volcanic slopes of the Hawaiian islands (Lipman et al, 1988;Moore et al, 1989), the large landslides from Tristan da Cunha (South Atlantic island) and from El Hierro (Canary islands) described by Holcomb and Searle (1991), the volcanic debris-avalanche along the submerged flank of the Fournaise volcano off the Reunion island (L&at et al, 1989;Cochonat et al, 1990), the giant submarine slide on the northern slope of Puerto Rico island and the giant submarine slump along the northern Chile continental slope (Li et al, 1991). All of the examples listed above are significant because of their large-scale submarine instabilities within consolidated materials.Topographic features indicating a mega submarine slide were mapped along the northern Peruvian margin, during the SEAPERC cruise in 1986 (Bourgois et al, 1986). Bathymetric data collected offshore Paita, between 5'25' and 5"5O'S, using the multibeam echo-sounder Seabeam allowed to document one seaward facing scarp located along the middle part of the margin.…”

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“…In 1986 these seismic data were completed by a 40 km wide swath of Seabeam bathymetry centered around the CDP3 line. Simultaneously four multichannel seismic profiles were acquired perpendicularly to the CDP3 line (Bourgois et al, 1986). The bathymetric data revealed the occurrence of two prominent curved scarps: the 400-700 m high upper slope scarp (USS) separating the upper slope from the middle slope area, and the 1000-1200 m high middle slope scarp (MSS), located 10 km seaward along the middle slope.…”

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“…The lower slope is characterized by a chaotic topography with highs and lows without preferred orientation, suggesting an accumulation of mass-wasted debris from the MSS (Bourgois et al, 1986(Bourgois et al, , 1988Von Huene et al, 1989;Duperret et al, 1993). From the interpreted additional seismic data, it was suggested that the USS represents the scarp of a detachment fault dipping 45" seaward (Bourgois et al, 1988). After reprocessing of the CDP3 line, including pre-stack migration (Von Huene and Miller, 1988), the middle part of the slope has been interpreted as a landward tilted block rotated along a major detachment fault, with massive collapse of the seaward part of the block (Von Huene et al, 1989).…”

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Slope instabilities at an active continental margin: large-scale polyphase submarine slides along the northern Peruvian margin, between 5 °S and 6 °S

et al. 1995

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A mega-submarine slide was evidenced along the Peruvian margin during a Seabeam survey of the R/V Charcot (Bourgois et al., 1986). The debris-slide was initially interpreted as the result of the slope failure occurring along a seaward curved scarp, and extending from east to west, along the line of maximum slope. Complementary bathymetric data obtained from the R/V Sonne survey conducted to the north and to the south of the previous surveyed area has resulted in the identification of large-scale polyphase submarine slides involving a total surface of about 1000 km', between latitudes 5"lSS and 6"05'S. Using Seabeam and Hydrosweep multibeam echosounder data in combination with deep-sea submersible observations, three distinct slope-failure types related to three main stages have been revealed. The three sliding phases occurred roughly along the same trend, orientated N230", and are therefore mainly controlled by the N80" orientation of the subducting Nazca plate.( 1) The first phase of slope failure is documented by a debris-avalanche deposit, which extends from the lower slope down to 5 km within the trench floor. The deposit originates from the northern wall of a wide valley located along the upper slope. (2) The second phase of slope failure is characterized by a debris-avalanche, with a crescent-shaped scar, located along the middle slope and a hummocky deposit covering the lower slope and extending up to 10 km across the trench. The volume of rock involved in this event is estimated to some 250 km3. The slope failure is assumed to be related to an oversteepening of the middle slope induced by a rollover deformation. (3) The third phase of slope failure corresponds to a translational sliding block and a toppling block with volumes of 6 km3 and 13 km3, respectively. The seismic energy produced during the seismic cycle has greatly increased fracturation and fluids buildup along the area previously weakened by a rollover fold. A restricted N-S folding is observed in the vicinity of the trench, to the north of the two debris-avalanche deposits. It may have formed in relation to the local compression limited to the subduction of the Nazca plate. Sliding and folding thus document the paradox between the compressive regime in the lower plate and the extensional regime in the upper part of the upper plate. IntroductionMost of the large-scale submarine landslides recognised worldwide occur either along intraplate volcanic alignments or along active continental margins. They include landslides along the steep submerged volcanic slopes of the Hawaiian islands (Lipman et al., 1988;Moore et al., 1989), the large landslides from Tristan da Cunha (South Atlantic island) and from El Hierro (Canary islands) described by Holcomb and Searle (1991), the volcanic debris-avalanche along the submerged flank of the Fournaise volcano off the Reunion island (L&at et al., 1989;Cochonat et al., 1990), the giant submarine slide on the northern slope of Puerto Rico island and the giant submarine slump along the northern Chile co...

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confidence: 99%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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Slope instabilities at an active continental margin: large-scale polyphase submarine slides along the northern Peruvian margin, between 5 °S and 6 °S

et al. 1995

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Fore‐arc seafloor unconformities and geology: Insight from 3‐D seismic geomorphology analysis, Peru

Calvès

Auguy

Lavaissière

et al. 2017

Geochem Geophys Geosyst

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New 3‐D seismic data collected over 4870 km2 in the 3°45′S–12°30′S Peruvian segment of the East Pacific subduction system image seafloor erosional surfaces that can be mapped across the fore‐arc basins. Fore‐arc 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 fore‐arc basins. We address this with the study of examples sourced from 3‐D 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 fore‐arc basins of South America and helps to highlight the importance of erosive surficial processes in subduction landscapes.

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Continental Margin Tectonics: Forearc Processes

Lundberg

Reed

1991

Reviews of Geophysics

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Seabeam and seismic reflection imaging of the tectonic regime of the Andean continental margin off Peru (4°S to 10°S)

Cited by 34 publications

References 12 publications

Slope instabilities at an active continental margin: large-scale polyphase submarine slides along the northern Peruvian margin, between 5 °S and 6 °S

Slope instabilities at an active continental margin: large-scale polyphase submarine slides along the northern Peruvian margin, between 5 °S and 6 °S

Fore‐arc seafloor unconformities and geology: Insight from 3‐D seismic geomorphology analysis, Peru

Continental Margin Tectonics: Forearc Processes

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