Debris Flows vs. Turbidity Currentsa Modeling Comparison of Their Dynamics and Deposits

2000 ◽  
Author(s):  
Lincoln F. Pratson ◽  
Jasim Imran ◽  
Gary Parker ◽  
James P. M. Syvitski ◽  
Eric Hutton
Keyword(s):  
Debris Flows ◽  
Turbidity Currents

Sedimentary facies on the rises and slopes of passive continental margins

1980 ◽  
Vol 294 (1409) ◽  
pp. 169-176 ◽  
Keyword(s):  
Sediment Transport ◽  
Debris Flows ◽  
Thermohaline Circulation ◽  
Dominant Role ◽  
Sedimentary Facies ◽  
Turbidity Currents ◽  
Continental Margins ◽  
Passive Margins ◽  
New Evidence

JOIDES drilling results provide new evidence concerning facies patterns on evolving passive margins that strengthens and extends hypotheses constructed from studies of morphology, seismic reflexion data and shallow samples on modern margins, and from field geologic studies of uplifted ancient margins. On the slopes and rise, gravity-controlled mechanisms - turbidity currents, debris flows, slides and the like - play the dominant role in sediment transport over the long term, but when clastic supplies are reduced, as for example during rapid transgressions, then oceanic sedimentation and the effects of thermohaline circulation become important. Sedimentary facies models used as the basis of unravelling tectonic complexities of some deformed margins, for example in the Mesozoic Tethys, may be too simplistic in the light of available data from modern continental margins.

Slow build-up of turbid currents triggered by a moderate earthquake in the Sea of Marmara

2020 ◽  
Author(s):  
Pierre Henry ◽  
M Sinan Özeren ◽  
Nurettin Yakupoğlu ◽  
Ziyadin Çakir ◽  
Emmanuel de Saint-Léger ◽  
...  
Keyword(s):  
Pressure Sensor ◽  
Debris Flows ◽  
Background Level ◽  
Signal Strength ◽  
Normal Operation ◽  
Turbidity Currents ◽  
Central Basin ◽  
Sea Of Marmara ◽  
Moderate Earthquake ◽  
Mud Flow

<p>Earthquake-induced submarine slope destabilization is known to cause debris flows and turbidity currents. These also interact with currents caused by tsunami and seiches resulting in deposits with specific sedimentological characteristics, turbidite-homogenites being a common example. Data on the deep-sea hydrodynamic events following earthquakes are, however, limited. An instrumented frame deployed at the seafloor in the Sea of Marmara Central Basin recorded some of the consequences of a magnitude 5.8 earthquake that occurred Sept 26, 2019 at 10-12 km depth without causing any significant tsunami. The instrumentation comprises a Digiquartz® pressure sensor recording at 5 s interval and a 1.9-2 MHz Doppler recording current meter set 1.5 m above the seafloor and recording at 1-hour interval. The device was deployed at 1184 m depth on the floor of the basin near the outlet of a canyon, 5 km from the epicenter. Chirp sediment sounder profiles indicate a depositional fan or lobe is present at this location. The passing of the seismic wave was recorded by the pressure sensor, but little other perturbation is recorded until 25 minutes later when the instrument, probably hit by a mud flow, tilts by 65° in about 15 seconds. Over the following 10 hours the tilted instrument records bursts of current of variable directions. The last burst appears to be the strongest with velocities in the 20-50 cm/s range, causing enough erosion to free the device from the mud and allowing the buoyancy attached to the upper part of the frame to straighten it back to its normal operation position. Then, the current, flowing down along the canyon axis, progressively decays to background level (≈2 cm/s) in 8 hours. Doppler signal backscatter strength is a proxy for turbidity, sensitive to sand-size suspended particles. Signal strength increased to high values during the event (max -7.6 dB from a background value of -40dB) and decayed over the next three days. These observations show that even a moderate earthquake can trigger a complex response involving mud flows and turbidity currents. We infer simultaneous slope failures at various locations may produce complex current patterns and cause build-up of kinetic energy over several hours.</p>

Silurian microbial associations from the Alexander terrane, Alaska

1993 ◽  
Vol 67 (5) ◽  
pp. 728-738 ◽  
Author(s):  
Constance M. Soja ◽  
Robert Riding
Keyword(s):  
Debris Flows ◽  
Turbidity Currents ◽  
Diverse Population ◽  
Microbial Assemblage ◽  
Microbial Associations ◽  
Transport And Mixing ◽  
Shelf Margin ◽  
Water Carbonate ◽  
Carbonate Deposits ◽  
Alexander Terrane

Silurian calcareous algae, cyanobacteria, and microproblematica are abundantly preserved in the Alexander terrane of southeastern Alaska. They represent a diverse population of calcified microbes that contributed to the formation of a variety of shallow- and deep-water carbonate deposits. Five associations are recognized on the basis of recurring groups of microbial taxa. These include a Girvanella-Tuxekanella association that formed oncoids and thick encrustations on skeletal grains in shelf environments. A Renalcis association predominated in a stromatoporoid-coral reef that developed at the incipient shelf margin on a crinoid-solenoporid shoal (“Solenopora” association). Other organic buildups are characterized by a Ludlovia association, which constructed skeletal stromatolite reefs, and by an Epiphyton-Sphaerina association that contributed to the formation of a stromatolitic mud mound. A mixed microbial assemblage reflects transport and mixing of shallow-water microbial biotas that were deposited by turbidity currents, debris flows, and slumps in a slope environment.

Influence of Salt Tectonics On Fault Displacements and Submarine Slope Failures from Algeria To Sardinia

2019 ◽  
Vol 25 (4) ◽  
pp. 318-330 ◽  
Author(s):  
Julia A. Yeakley ◽  
Abdul Shakoor ◽  
William Johnson
Keyword(s):  
Debris Flows ◽  
Average Rate ◽  
Plate Boundary ◽  
Western Mediterranean ◽  
Turbidity Currents ◽  
Salt Tectonics ◽  
Slope Failures ◽  
Submarine Slope ◽  
Lateral Extent ◽  
Pipeline Route

ABSTRACT We used previously obtained marine geophysical and geotechnical data for the proposed Galsi pipeline route from Algeria to Sardinia to analyze the buried salt distribution, rates of fault displacements, and frequency and lateral extent of submarine slope failures. Crossing the convergent African/Nubian–European plate boundary, the southern section of the pipeline route traverses continental shelves and slopes of Algeria and Sardinia as well as the Algerian abyssal plain of the western Mediterranean. Deeply buried Messinian-aged salt is present throughout this area. Being less dense and more buoyant than the overburden sediment, the salt tends to flow upward to form diapiric structures that, in turn, result in the formation of faults and landslides in the overlying sediment. Measured offsets from seismic profiles of different resolutions were compared with predicted sediment age at depth of each offset, yielding an average rate of fault displacement of 1.5 cm/kiloyear (ky). The highest rates of displacement are along the Cagliari slope near Sardinia (2.5-2.7 cm/ky) and near the convergent plate boundary (2.3 cm/ky). Utilizing the same geophysical data, the frequency and lateral extent of submarine slope failures in the study area can also be linked to the distribution of salt and the influence of salt tectonics. Turbidity currents and hyperpycnal flows are present within the Algerian basin, whereas local debris flows, landslide runouts, and channelized debris flows are present along the Sardinian slope. The low sedimentation rates, determined in this study, suggest that the most recent slope failures related to salt tectonics occurred more than 12,000 years ago.

Pleistocene marine kettle-fill deposits near Ottawa, Canada

1980 ◽  
Vol 17 (9) ◽  
pp. 1236-1245 ◽  
Author(s):  
M. Hayward ◽  
H. M. French
Keyword(s):  
Marine Environment ◽  
Debris Flows ◽  
Slope Instability ◽  
Turbidity Currents ◽  
Ice Melt ◽  
Sand And Gravel

Exposures at several localities in the Ottawa region reveal Champlain Sea deposits filling depressions on what were formerly submerged surfaces of Wisconsin sand and gravel ridges. The deposits, referred to as "kettle fill," constitute materials eroded from the ridges in a marine environment and redeposited in ice-melt depressions or kettle holes. Processes responsible for the deposition of the sediment appear to include debris flows and small turbidity currents initiated by wave washing and slope instability. The dimensions of the depressions, their depth in relation to the falling wave base, and the steepness of the flanks were important factors controlling sedimentation. The kettle-fill facies comprise diamicton (pebbly mud), gravel, sand, and lutite.

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