Preconditioning and triggering of offshore slope failures and turbidity currents revealed by most detailed monitoring yet at a fjord-head delta

Clare, Michael; Clarke, John E. Hughes; Talling, Peter J.; Cartigny, Matthieu; Pratomo, Danar Guruh

doi:10.1016/j.epsl.2016.06.021

Cited by 139 publications

(135 citation statements)

References 37 publications

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“…Cyclic steps are sediment waves that migrate upstream and are formed by turbidity currents that recurrently undergo hydraulic jumps (Kostic et al, ). These types of sediment waves are known to be present on active delta slopes (Clare et al, ; Fricke et al, ; Hughes Clarke, ; Kostic et al, ; Normandeau et al, ); their presence indicates active processes (e.g., Hughes Clarke, ; Normandeau et al, ; Smith et al, ). Therefore, the presence of sediment waves indicates that turbidity currents occur on the delta slopes (i.e., active deltas) although their frequency is unknown.…”

Section: Methodsmentioning

confidence: 99%

Retreat Pattern of Glaciers Controls the Occurrence of Turbidity Currents on High‐Latitude Fjord Deltas (Eastern Baffin Island)

et al. 2019

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Glacier and ice sheet mass loss as a result of climate change is driving important coastal changes in Arctic fjords. Yet limited information exists for Arctic coasts regarding the influence of glacial erosion and ice mass loss on the occurrence and character of turbidity currents in fjords, which themselves affect delta dynamics. Here we show how glacial erosion and the production of meltwaters and sediments associated with the melting of retreating glaciers control the generation of turbidity currents in fjords of eastern Baffin Island (Canada). The subaqueous parts of 31 river mouths along eastern Baffin Island were mapped by high‐resolution swath bathymetry in order to assess the presence or absence of sediment waves formed by turbidity currents on delta fronts. By extracting glaciological and hydrological watershed characteristics of these river mouths, we demonstrate that the presence and areal extent of glaciers are a key control for generating turbidity currents in fjords. However, lakes formed upstream during glacial retreat significantly alter the course of sediment routing to the deltas by forming temporary sinks, leading to the cessation of turbidity currents in the fjords. Due to the different deglaciation stages of watersheds in eastern Baffin Island, we put these results into a temporal framework of watershed deglaciation to demonstrate how the retreat pattern of glaciers, through the formation and filling of proglacial lakes, affects the turbidity current activity of deltas.

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Section: Methodsmentioning

confidence: 99%

Retreat Pattern of Glaciers Controls the Occurrence of Turbidity Currents on High‐Latitude Fjord Deltas (Eastern Baffin Island)

et al. 2019

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“…Five delta‐lip failures occurred over 135 days in 2011. The first two lip failures coincided with unusually low tides, whilst the final three failures occurred a few hours after peaks in river discharge (Clare et al ., ). This suggests that failure was triggered by unusually rapid delta‐lip progradation during river discharge peaks, and processes associated with low tides.…”

Section: Summary Of Previous Direct Monitoring Of Flow Processesmentioning

confidence: 97%

“…Water discharge from the Squamish River increases from ca 100 m 3 sec −1 during the winter, to ca 500 m 3 sec −1 during a four‐month summer freshet period, primarily due to snow melt. Turbidity current activity tends to initiate with discharges in excess of 300 to 350 m 3 (Hughes Clarke, ; Clare et al ., ). Occasional sharp peaks in river discharge reach ca 1000 m 3 sec −1 during the freshet (Hughes Clarke et al ., ).…”

Section: Study Area: Squamish Delta and Howe Soundmentioning

confidence: 99%

“…It was found that the proximal channels and associated lobes were highly active. Two types of event were defined; large‐scale failures of the delta lip, and numerous events that caused bedform movement which were triggered by smaller failures of sediment settling from river plumes (Hughes Clarke et al ., ; Clare et al ., ; Hizzett et al ., ).…”

Section: Summary Of Previous Direct Monitoring Of Flow Processesmentioning

confidence: 99%

“…This suggests that failure was triggered by unusually rapid delta‐lip progradation during river discharge peaks, and processes associated with low tides. Such processes at low tide may include expansion of gas bubbles within the sediment, or focussing of river discharge (and hence more rapid delta‐lip progradation) (Hughes Clarke et al ., ; Clare et al ., ). Sediment from the largest delta‐lip failures sometimes infilled the proximal channels on the delta front.…”

Section: Summary Of Previous Direct Monitoring Of Flow Processesmentioning

confidence: 99%

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How turbidity current frequency and character varies down a fjord‐delta system: Combining direct monitoring, deposits and seismic data

et al. 2019

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Submarine turbidity currents are one of the most important processes for moving sediment across our planet; they are hazardous to offshore infrastructure, deposit petroleum reservoirs worldwide, and may record tsunamigenic landslides. However, there are few studies that have monitored these submarine flows in action, and even fewer studies that have combined direct monitoring with longer‐term records from core and seismic data of deposits. This article provides one of the most complete studies yet of a turbidity current system. The aim here is to understand what controls changes in flow frequency and character along the turbidite system. The study area is a 12 km long delta‐fed fjord (Howe Sound) in British Columbia, Canada. Over 100 often powerful (up to 2 to 3 m sec−1) events occur each year in the highly‐active proximal channels, which extend for 1 to 2 km from the delta lip. About half of these events reach the lobes at the channel mouths. However, flow frequency decreases rapidly once these initially sand‐rich flows become unconfined, and only one to five flows run out across the mid‐slope each year. Many of these sand‐rich, channelized, delta‐sourced flows therefore dissipated over a few hundred metres, once unconfined, rather than eroding and igniting. Upflow migrating bedforms indicate that supercritical flow dominated in the proximal channels and lobes, and also across the unconfined mid‐slope. These supercritical flows deposited thick sand beds in proximal channels and lobes, but thinner and finer beds on the unconfined mid‐slope. The distal flat basin records far larger volume and more hazardous events that have a recurrence interval of ca 100 years. This study shows how sand‐rich delta‐fed flows dissipate rapidly once they become unconfined, that supercritical flows dominate in both confined and unconfined settings, and how a second type of more hazardous, and much less frequent event is linked to a different scale of margin failure.

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Durable Terrestrial Bedrock Predicts Submarine Canyon Formation

Smith

Finnegan

Mueller

et al. 2017

Geophysical Research Letters

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Though submarine canyons are first‐order topographic features of Earth, the processes responsible for their occurrence remain poorly understood. Potentially analogous studies of terrestrial rivers show that the flux and caliber of transported bedload are significant controls on bedrock incision. Here we hypothesize that coarse sediment load could exert a similar role in the formation of submarine canyons. We conducted a comprehensive empirical analysis of canyon occurrence along the West Coast of the contiguous United States which indicates that submarine canyon occurrence is best predicted by the occurrence of durable crystalline bedrock in adjacent terrestrial catchments. Canyon occurrence is also predicted by the flux of bed sediment to shore from terrestrial streams. Surprisingly, no significant correlation was observed between canyon occurrence and the slope or width of the continental shelf. These findings suggest that canyon incision is promoted by greater yields of durable terrestrial clasts to the shore.

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Preconditioning and triggering of offshore slope failures and turbidity currents revealed by most detailed monitoring yet at a fjord-head delta

Cited by 139 publications

References 37 publications

Retreat Pattern of Glaciers Controls the Occurrence of Turbidity Currents on High‐Latitude Fjord Deltas (Eastern Baffin Island)

Retreat Pattern of Glaciers Controls the Occurrence of Turbidity Currents on High‐Latitude Fjord Deltas (Eastern Baffin Island)

How turbidity current frequency and character varies down a fjord‐delta system: Combining direct monitoring, deposits and seismic data

Durable Terrestrial Bedrock Predicts Submarine Canyon Formation

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