Evidence of a turbidity current in Monterey Submarine Canyon associated with the 1989 Loma Prieta earthquake

Garfield, Newell; Rago, Thomas A.; Schnebele, Kurt J.; Collins, Curtis A.

doi:10.1016/0278-4343(94)90112-0

Cited by 41 publications

(29 citation statements)

References 10 publications

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“…Sediment budgets and transport processes in Monterey Canyon have been assessed indirectly through littoral cell analysis (Best and Griggs, 1991) and canyon geomorphology (Paull et al, 2005;Smith et al, 2005), and directly via current and turbidity measurements or by documenting the unintentional, rapid, down-canyon movement of "moored" instruments (Garfield et al, 1994;Paull et al, 2003;Xu et al, 2004). A synthesis of those studies and a growing body of unpublished data demonstrate that Monterey Canyon presently conveys sand and gravel part-way along its axis via sediment transport events that occur several times annually.…”

Section: Sediment Budget and Transport Processesmentioning

confidence: 99%

Twenty-nine months of geomorphic change in upper Monterey Canyon (2002–2005)

et al. 2007

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Section: Sediment Budget and Transport Processesmentioning

confidence: 99%

Twenty-nine months of geomorphic change in upper Monterey Canyon (2002–2005)

et al. 2007

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“…However, flooding events with sufficient magnitude to produce a hyperpycnal flow have not occurred during the time when there has been monitoring equipment within Monterey Canyon. In one instance, an event in the upper canyon was coincident with strong ground shaking associated with the installation of a new bridge foundation near the canyon head (Paull et al, 2010a), and an additional event may have been triggered by the 1989 Loma Prieta (M W 7.1) earthquake (Garfield et al, 1994). No empirical observations exist for what triggers the less frequent and larger volume and longer run-out flows that exit the canyon every~100 years.…”

Section: Monterey Canyon Offshore Californiamentioning

confidence: 99%

How are subaqueous sediment density flows triggered, what is their internal structure and how does it evolve? Direct observations from monitoring of active flows

Talling

Paull

Piper

2013

Earth-Science Reviews

209

184

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Subaqueous sediment density flows are one of the volumetrically most important processes for moving sediment across our planet, and form the largest sediment accumulations on Earth (submarine fans). They are also arguably the most sparely monitored major sediment transport processes on our planet. Significant advances have been made in documenting their timing and triggers, especially within submarine canyons and delta-fronts, and freshwater lakes and reservoirs, but the sediment concentration of flows that run out beyond the continental slope has never been measured directly. This limited amount of monitoring data contrasts sharply with other major types of sediment flow, such as river systems, and ensure that understanding submarine sediment density flows remains a major challenge for Earth science. The available monitoring data define a series of flow types whose character and deposits differ significantly. Large (N 100 km 3 ) failures on the continental slope can generate fast-moving (up to 19 m/s) flows that reach the deep ocean, and deposit thick layers of sand across submarine fans. Even small volume (0.008 km 3 ) canyon head failures can sometimes generate channelised flows that travel at N 5 m/s for several hundred kilometres. A single event off SE Taiwan shows that river floods can generate powerful flows that reach the deep ocean, in this case triggered by failure of recently deposited sediment in the canyon head. Direct monitoring evidence of powerful oceanic flows produced by plunging hyperpycnal flood water is lacking, although this process has produced shorter and weaker oceanic flows. Numerous flows can occur each year on river-fed delta fronts, where they can generate up-slope migrating crescentic bedforms. These flows tend to occur during the flood season, but are not necessarily associated with individual flood discharge peaks, suggesting that they are often triggered by delta-front slope failures. Powerful flows occur several times each year in canyons fed by sand from the shelf, associated with strong wave action. These flows can also generate up-slope migrating crescentic bedforms that most likely originate due to retrogressive breaching associated with a dense near-bed layer of sediment. Expanded dilute flows that are supercritical and fully turbulent are also triggered by wave action in canyons. Sediment density flows in lakes and reservoirs generated by plunging river flood water have been monitored in much greater detail. They are typically very dilute (b 0.01 vol.% sediment) and travel at b 50 cm/s, and are prone to generating interflows within the density stratified freshwater. A key objective for future work is to develop measurement techniques for seeing through overlying dilute clouds of sediment, to determine whether dense near-bed layers are present. There is also a need to combine monitoring of flows with detailed analyses of flow deposits, in order to understand how flows are recorded in the rock record. Finally, a source-to-sink approach is needed because the character of subm...

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“…Numerous studies documented the transit of gravity driven flows down, for instance in the Monterey, Capbreton, Kaikoura or Zaire canyons (Garfield et al, 1994;Khripounoff et al, 2003;Lewis and Barnes, 1999;Paull et al, 2003). However, these canyons are either directly connected to a river system or located close to the shoreline and therefore under the influence of inner shelf and/or fluvial dynamics (Liu and Lin, 2004;Mullenbach and Nittrouer, 2000;Mullenbach et al, 2004;Puig et al, 2003;Segall et al, 1989;Shanmugam, 2003;Shepard and Marshall, 1973;Snyder and Carson, 1986;Thorbjarnarson et al, 1986;Xu et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

Massive sand beds attributed to deposition by dense water cascades in the Bourcart canyon head, Gulf of Lions (northwestern Mediterranean Sea)

et al. 2006

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International audienceNowadays, the Gulf of Lions continental shelf and slope are under the influence of dense water cascading, wind-induced bottom currents and the geostrophic Northern Current. In order to characterize sedimentary activity at the shelf break, several interface and piston cores were taken in the Bourcart canyon head and a current meter equipped with temperature, conductivity, pressure and turbidity sensors was moored during the 2003–2004 winter season. Even if the canyon is not connected directly to continental sources since Last Glacial Maximum, detailed grain size, X-ray and sediment facies analysis of interface cores show that down to 350 m water depth, the canyon head is blanketed by up to 1.5 m of structureless muddy medium-grained sand. 210Pbexc activity measurements demonstrate present day sedimentary activity of the canyon head. Time series of currents with peak velocity reaching 0.37 m/s, suspended sediment concentration and temperature indicate that dense water cascading is the main process allowing the reworking, transport and accumulation of sand within the canyon head, even though winter 2003–2004 was characterized by low cascading events compared to other years. These sand beds, called “cascadite” constitute a new type of deposit that differs from other typical slope deposits (turbidites, hyperpycnites, contourites) in terms of flow duration and sedimentological characteristics. They are similar to shallow water contourites. They might be time-equivalent to the recent turbidites described throughout the deep western Gulf of Lions basin

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Evidence of a turbidity current in Monterey Submarine Canyon associated with the 1989 Loma Prieta earthquake

Cited by 41 publications

References 10 publications

Twenty-nine months of geomorphic change in upper Monterey Canyon (2002–2005)

Twenty-nine months of geomorphic change in upper Monterey Canyon (2002–2005)

How are subaqueous sediment density flows triggered, what is their internal structure and how does it evolve? Direct observations from monitoring of active flows

Massive sand beds attributed to deposition by dense water cascades in the Bourcart canyon head, Gulf of Lions (northwestern Mediterranean Sea)

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