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

Abstract

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...

A review of sediment distributions and processes in Oligo-Miocene ramps of southern Italy and Malta (Mediterranean divide)

“…Although tsunamis have been cited as causing similar structures (Houtz & Wellman 1962), which might subsequently infill with 'tempestite deposits' (Kelling & Mullins 1975), the general configuration and internal structure of these bodies is more consistent with slide structures described by Lewis (1971) and Duperret et al (1995), from offshore seismic profiles, as detached sediment sheets. Similar slide structures have been described from other modern settings by Wilhelm & Ewing (1972), Prior & Coleman (1979) and Mullins & Heath (1984).…”

Basin‐wide mass‐wasting complexes as markers of the Oligo‐Miocene foredeep‐accretionary wedge evolution in the Northern Apennines, Italy

“…Ritger et al, 1987;Orange & Breen, 1992;Duperret et al, 1992;Bohrmann et al, 2002;Choconat et al, 2002;Henry et al, 2002) where £uids are pumped by tectonic-induced compaction and can reach the sea£oor through di¡erent routes channelled along permeable bed packages, thrust faults, gravity faults (slide scar), joint fractures (e.g. Ritger et al, 1987;Orange & Breen, 1992;Duperret et al, 1992;Bohrmann et al, 2002;Choconat et al, 2002;Henry et al, 2002) where £uids are pumped by tectonic-induced compaction and can reach the sea£oor through di¡erent routes channelled along permeable bed packages, thrust faults, gravity faults (slide scar), joint fractures (e.g.…”

Late Miocene seep-carbonates and fluid migration on top of the Montepetra intrabasinal high (Northern Apennines, Italy): Relations with synsedimentary folding

“…Fluid expulsion at the sea floor is evidenced by: 1) specialized seep ecosystems (e.g., Sibuet and Olu, 1998;Van Dover et al, 2003), 2) authigenic carbonates (e.g., Aiello, 2005;Teichert et al, 2005;Campbell et al, 2008), 3) enhanced slope instability (Bohrmann et al, 2002), and 4) mud diapirs and volcanoes (Orange and Breen, 1992;Greinert et al, 2001;Kastner, 2001;Torres et al, 2002;Mazurenko and Soloviev, 2003;Moerz et al, 2005). Fluid emission along active continental margins could be located in erosive structures, such as canyons, head zones and scars of slides and slumpings (Duperret et al, 1995;Von Rad et al, 2000;Majima et al, 2005), or on relatively elevated structures, such as diapir-related mounds and mud volcanoes (Lance et al, 1998;Aloisi et al, 2000;Kopf et al, 2001;Mazurenko et al, 2002;Han et al, 2004), and at the top of anticlines and fault-controlled ridges (Lallemand et al, 1992;Suess et al, 1998Suess et al, , 1999Orphan et al, 2004).…”