Evidence of slope instability in the Southwestern Adriatic Margin

Abstract. The Southwestern Adriatic Margin (SAM) shows evidence of widespread failure events that generated slide scars up to 10 km wide and extensive slide deposits with run out distances greater than 50 km. Chirp-sonar profiles, side-scan sonar mosaics, multibeam bathymetry and sediment cores document that the entire slope area underwent repeated failures along a stretch of 150 km and that mass-transport deposits, covering an area of 3320 km2, are highly variable ranging from blocky slides to turbidites, and lay on the lower slope and in the basin. The SAM slope between 300–700 m is impacted by southward bottom currents shaping sediment drifts (partly affected by failure) and areas of dominant erosion of the seafloor. When slide deposits occur in areas swept by bottom currents their fresh appearence and their location at seafloor may give the misleading impression of a very young age. Seismic-stratigraphic correlation of these deposits to the basin floor, however, allow a more reliable age estimate through sediment coring of the post-slide unit. Multiple buried failed masses overlap each other in the lower slope and below the basin floor; the most widespread of these mass-transport deposits occurred during the MIS 2-glacial interval on a combined area of 2670 km2. Displacements affecting Holocene deposits suggest recent failure events during or after the last phases of the last post-glacial eustatic rise. Differences in sediment accumulation rates at the base or within the sediment drifts and presence of downlap surfaces along the slope and further in the basin may provide one or multiple potential weak layers above which widespread collapses take place. Neotectonic activity and seismicity, together with the presence of a steep slope, represent additional elements conducive to sediment instability and failure along the SAM. Evidence of large areas still prone to failure provides elements of tsunamogenic hazard.

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Slope Instability And Mass Transport Deposits On The Godavari River Delta, East Indian Margin From A Regional Geological Perspective

Submarine Mass Movements and Their Consequences ◽

10.1007/978-1-4020-6512-5_3 ◽

2007 ◽

pp. 19-27 ◽

Cited By ~ 3

Author(s):

C. F. Forsberg ◽

A. Solheim ◽

T. J. Kvalstad ◽

R. Vaidya ◽

S. Mohanty

Keyword(s):

Mass Transport ◽

River Delta ◽

Slope Instability ◽

East Indian ◽

Godavari River ◽

Mass Transport Deposits

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Syndepositional tectonics and mass-transport deposits control channelized, bathymetrically complex deep-water systems (Aínsa depocenter, Spain)

Journal of Sedimentary Research ◽

10.2110/jsr.2020.38 ◽

2020 ◽

Vol 90 (7) ◽

pp. 729-762

Author(s):

Daniel E. Tek ◽

Miquel Poyatos-Moré ◽

Marco Patacci ◽

Adam D. McArthur ◽

Luca Colombera ◽

...

Keyword(s):

Mass Transport ◽

Deep Water ◽

Tectonic Setting ◽

Water Systems ◽

Tectonic Structures ◽

Lateral Confinement ◽

Facies Associations ◽

Active Tectonic ◽

Basin Floor ◽

Mass Transport Deposits

ABSTRACT The inception and evolution of channels in deep-water systems is controlled by the axial gradient and lateral confinement experienced by their formative flows. These parameters are often shaped by the action of tectonic structures and/or the emplacement of mass-transport deposits (MTDs). The Arro turbidite system (Aínsa depocenter, Spanish Pyrenees) is an ancient example of a deep-water channelized system from a bathymetrically complex basin, deposited in an active tectonic setting. Sedimentologic fieldwork and geologic mapping of the Arro system has been undertaken to provide context for a detailed study of three of the best-exposed outcrops: Sierra de Soto Gully, Barranco de la Caxigosa, and Muro de Bellos. These locations exemplify the role of confinement in controlling the facies and architecture in the system. Sedimentologic characterization of the deposits has allowed the identification of fifteen facies and eight facies associations; these form a continuum and are non-unique to any depositional environment. However, architectural characterization allowed the grouping of facies associations into four depositional elements: i) weakly confined, increasing-to-decreasing energy deposits; ii) progradational, weakly confined to overbank deposits; iii) alternations of MTDs and turbidites; iv) channel fills. Different styles of channel architecture are observed. In Barranco de la Caxigosa, a master surface which was cut and subsequently filled hosts three channel stories with erosional bases; channelization was enhanced by quasi-instantaneous imposition of lateral confinement by the emplacement of MTDs. In Muro de Bellos, the inception of partially levee-confined channel stories was enhanced by progressive narrowing of the depositional fairway by tectonic structures, which also controlled their migration. Results of this study suggest that deep-water channelization in active tectonic settings may be enhanced or hindered due to: 1) flow interaction with MTD-margin topography or; 2) MTD-top topography; 3) differential compaction of MTDs and/or sediment being loaded into MTDs; 4) formation of megascours by erosive MTDs; 5) basin-floor topography being reset by MTDs. Therefore, the Arro system can be used as an analog for ancient subsurface or outcrop of channelized deposits in bathymetrically complex basins, or as an ancient record of deposits left by flow types observed in modern confined systems.

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Evaluating the sealing potential of young and thin mass-transport deposits: Lake Villarrica, Chile

Geological Society London Special Publications ◽

10.1144/sp500-2019-155 ◽

2019 ◽

Vol 500 (1) ◽

pp. 129-146 ◽

Cited By ~ 2

Author(s):

Jasper Moernaut ◽

Gauvain Wiemer ◽

Achim Kopf ◽

Michael Strasser

Keyword(s):

Shear Strength ◽

Mass Transport ◽

Pore Pressure ◽

Sediment Cores ◽

Free Fall ◽

Undrained Shear Strength ◽

Excess Pore Pressure ◽

Minor Role ◽

Mass Transport Deposits ◽

Undrained Shear

AbstractSubaqueous mass-transport deposits (MTDs) can be important elements in hydrocarbon systems, forming potential reservoirs or seals. Most research has targeted outcrops or moderately to deeply buried MTDs and, therefore, the petrophysical properties of near-seafloor MTDs, and their influence in the trapping and release of shallow fluids, is poorly studied. Here, we investigate shallow MTDs in Lake Villarrica (Chile) by combining sub-bottom profiles, free-fall penetrometer data, pore pressure dissipation tests and geotechnical properties of sediment cores. Low undrained shear strength under a surficial MTD indicates underconsolidation caused by sudden loading and rapid sealing. Larger, buried MTDs show acoustic signatures of free gas at their base, indicating effective sealing. This is supported by degassing core gaps just below MTDs and by excess pore pressure ratios c. 30–70% within MTDs. Acoustic windows below rafted blocks suggest local fluid escape. MTDs exhibit elevated undrained shear strength and reduced porosity compared to surrounding sediments, but are comparable to upslope source sequences. This suggests that MTD sealing capacity in Villarrica relates to the apparently overconsolidated nature of the slope sequence, leaving a minor role for shear densification. This study shows that shallow MTDs can form a relatively rapid seal for fluid migration, locally degraded by rafted blocks.

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Sediment budget in a recently glaciated western Norwegian fjord

10.5194/egusphere-egu2020-21537 ◽

2020 ◽

Author(s):

Thomas Thuesen ◽

Haflidi Haflidason ◽

William Helland-Hansen ◽

Atle Nesje ◽

Amalie Krog Klette ◽

...

Keyword(s):

High Resolution ◽

Mass Transport ◽

Debris Flows ◽

3D Visualization ◽

Sediment Cores ◽

Rock Avalanche ◽

Ct Scanning ◽

Last Deglaciation ◽

Norwegian Fjord ◽

Mass Transport Deposits

Western Norwegian fjord-valley systems represent archives of changes in sedimentary processes, and typically exhibit a pronounced change in depositional environment related to the transition from glacial to interglacial conditions. During a glacial situation, the fjord-valley system is emptied of its sediments, indicating that most sediments present in the fjord today, was deposited during and after the retreat of the last deglaciation. The purpose of our investigations is to gain a better understanding of the volumes and frequencies of mass transport deposits (subaquatic mass movements such as mass flows, debris flows, slides, slumps, and turbidites) in a recently glaciated fjord-valley system since the deglaciation (approx. 11 700 years BP) by looking at Fj&#230;rlandsfjorden, a tributary fjord of Sognefjorden in western Norway. The fjord-valley system consists of steep hillslopes and deep fjord basins with reliefs of up to 1600 meters. Jostedalsbreen, the largest glacier on mainland Europe (ca. 473 km2), currently feeds into the catchment of the fjord basin.Here we present results from a cruise with R/V G.O. Sars in 2018, where sediment cores, TOPAS seismic profiles and bathymetric data were collected from Fj&#230;rlandsfjorden. The integration of high-resolution seismic (<30 cm vertical resolution) and bathymetry (3-5 m resolution) allows us to estimate the total volume of sediments within a fjord setting. By revealing when and how the sediments are deposited, we can establish sedimentation rates with a high spatial and temporal resolution within the fjord basin. X-ray Computed Tomography (CT-scanning) has been particularly useful to characterize sedimentary deposits as it allows for 3D visualization and analysis with ultra-high-resolution (50 &#956;m voxel size) allowing us to see individual silt-sized grains in the sediment cores.Seismic data reveal that the Fj&#230;rlandsfjorden basin infill consists of basal till, overlain by a thick, acoustically well-laminated glacimarine unit (up to a maximum thickness of ~105 meters thickness), occasionally disrupted by acoustically transparent lenses interpreted to be mass transport deposits (rock avalanches and debris flows). A 2-3 m thick hemipelagic unit drapes the glacimarine unit. Results reveal that ~90 % of the total sediment volume within the fjord basins was deposited as meltwater plumes during the retreat (mainly calving along the fjord) of the margin of the last glacial ice sheet. The retreat began at the mouth of Sognefjorden at the termination of the Younger Dryas Chronozone around 11 700 cal. yrs BP, to a frontal position at the head of Fj&#230;rlandsfjorden around 10 700 cal. yrs BP. The remaining volume of sediments are divided into mass transport deposits (MTDs) such as avalanches, debris flows, and flood-related turbidites as well as hemipelagic sedimentation. The largest MTD is a massive rock avalanche measuring up to 5 million m3 that most likely caused a large tsunami when it occurred.

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Giant mass-transport deposits in the southern Scotia Sea (Antarctica)

Geological Society London Special Publications ◽

10.1144/sp477.2 ◽

2018 ◽

Vol 477 (1) ◽

pp. 195-205 ◽

Cited By ~ 1

Author(s):

Luis Somoza ◽

Teresa Medialdea ◽

Francisco J. González

Keyword(s):

Mass Transport ◽

Regional Scale ◽

Slope Instability ◽

Continental Margins ◽

Scotia Sea ◽

Swath Bathymetry ◽

Diagenetic Alteration ◽

Silica Diagenesis ◽

Seismic Sections ◽

Mass Transport Deposits

AbstractOn the basis of 2D multichannel and very-high-resolution seismic data and swath bathymetry, we report a sequence of giant mass-transport deposits (MTDs) in the Scan Basin (southern Scotia Sea, Antarctica). MTDs with a maximum thickness of c. 300 m extend up to 50 km from the Discovery and Bruce banks towards the Scan Basin. The headwall area consists of multiple U-shaped scars intercalated between volcanic edifices, up to 250 m high and 7 km wide, extending c. 14 km downslope from 1750 to 2900 m water depth. Seismic sections show that these giant MTDs are triggered by the intersection between diagenetic fronts related to silica transformation and vertical fluid-flow pipes linked to magmatic sills emplaced within the sedimentary sequence of the Scan Basin. This work supports that the diagenetic alteration of siliceous sediments is a possible cause of slope instability along world continental margins where bottom-simulating reflectors related to silica diagenesis are present at a regional scale.

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Late Cenozoic shelf delta development and Mass Transport Deposits in the Dutch offshore area – results of 3D seismic interpretation

Netherlands Journal of Geosciences – Geologie en Mijnbouw ◽

10.1017/s0016774600000391 ◽

2012 ◽

Vol 91 (4) ◽

pp. 591-608 ◽

Cited By ~ 7

Author(s):

A. Benvenuti ◽

H. Kombrink ◽

J.H. ten Veen ◽

D.K. Munsterman ◽

F. Bardi ◽

...

Keyword(s):

Mass Transport ◽

Sea Level ◽

North Sea ◽

Sediment Supply ◽

Slope Instability ◽

Shear Surface ◽

Southern North Sea ◽

Basal Shear ◽

Mass Transport Deposits ◽

High Sediment

AbstractIn this study, seismic stratigraphic criteria have been used to characterise the evolution of the Southern North Sea (SNS) shelf-delta system that progressively filled the Southern North Sea basin during Plio-Pleistocene times. Based on the prograding and down-stepping architecture of the shelf-delta sequence it is inferred that deposition occurred during a time of high sediment supply and overall sea-level lowering. During this time the delta slopes failed several times, creating at least 30 internally coherent Mass Transport Deposits (MTDs) mainly grouped in common areas, affecting the same clinoform set and partially sharing the basal shear surface (groups of MTDs). The most important features of the studied MTDs are 1) the dominance of brittle deformation; 2) the small amount of material removal from the headwall domain (lack of completely depleted areas above the basal shear surface); and 3) the lack of an emergent toe domain above the un-failed sediment located basinward, although proper confining geometries for the MTD are not detected. Therefore, the studied MTDs can neither be classified as frontally confined nor as frontally emergent but they are a new intermediate type of submarine landslides which has not been described before. These characteristics suggest that the mass movement ceased relatively soon after initiation of failure. Incisions on top of the MTDs suggest the presence of erosive flows. These flows were probably generated due to a concentration of the drainage in the negative morphology the failure event left behind in the upper sector of the slope. The stronger progradational character of the reflections on top of MTDs confirms a concentration of drainage after the erosional phase too.The interplay between high sediment supply and constant or even decreasing accommodation space (caused by constant or decreasing sea-level) is supposed to be the main precondition for slope instability for most of the MTDs in this study area. Slope failures themselves can also be considered a preconditioning factor by the creation of local very high sedimentation rates (see groups of MTDs). Salt-induced seismicity and storm waves' effect superimposed on high frequency sea level fall are considered the most important triggering factors.

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