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

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.

Slumps Mass-Transport Deposits in the Brazilian Continental Margin Deep Water: Offshore Potiguar Basin, NE Brazil.

2020 ◽  
Author(s):  
Yoe Perez ◽  
Julia Fonseca ◽  
Helenice Vital ◽  
Andre Silva ◽  
David Castro
Keyword(s):  
Mass Transport ◽  
Continental Slope ◽  
Continental Margin ◽  
Deep Water ◽  
Negative Impact ◽  
Water Area ◽  
Passive Margin ◽  
Rift System ◽  
Potiguar Basin ◽  
Mass Transport Deposits

<p>The Brazilian Continental Margin (BEM) deep-water regions contain important geological features that need advance in their characterization. Mass-transport deposits (MTD) are important not only by their significance in the sedimentary but also because of their negative impact economically. A slump is a coherent mass of sediment that moves on a concave-up glide plane and undergoes rotational movements causing internal deformation and one of the basic types of MTD. The study area comprises part of the offshore Potiguar Basin in NE Brazil, on the distal eastern portion of the Touros High and Fernando de Noronha Ridge. This portion of the Potiguar Basin comprises a transform rift system that has evolved into a continental passive margin. This basin represents an important location related to the breakup between South America and Africa. The database used in this work included 2D post-stack time-migrated seismic profiles from the Brazilian Agency of Petroleum, Natural Gas, and Biofuels (ANP). The slumps reflectors are identified on the continental shelf profiles in form of present clinoform configuration, medium to high continuity, high amplitudes, and medium to high frequencies, representing a sigmoidal oblique complex prograding reflector. The slump scars at the continental slope indicate that this is a gravitationally unstable area that will eventually collapse, resulting in erosional features on the continental slope and deposition on the continental rise. Our results provide some insights regarding MDT slumps sedimentary evolution in the BEM deep water area as well as their interrelation with other sedimentary deposits.</p>

scholarly journals Evidence of slope instability in the Southwestern Adriatic Margin

2006 ◽  
Vol 6 (1) ◽  
pp. 1-20 ◽  
Author(s):  
D. Minisini ◽  
F. Trincardi ◽  
A. Asioli
Keyword(s):  
Mass Transport ◽  
Sediment Cores ◽  
Sediment Accumulation ◽  
Slope Instability ◽  
Stratigraphic Correlation ◽  
Bottom Currents ◽  
Sediment Drifts ◽  
Basin Floor ◽  
Mass Transport Deposits ◽  
Lower Slope

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.

Influence of mass transport deposit (MTD) surface topography on deep-water deposition: an example from a predominantly fine-grained continental margin, New Zealand

2020 ◽  
Vol 500 (1) ◽  
pp. 147-171 ◽  
Author(s):  
Suzanne Bull ◽  
Greg H. Browne ◽  
Malcolm J. Arnot ◽  
Lorna J. Strachan
Keyword(s):  
New Zealand ◽  
Mass Transport ◽  
Surface Topography ◽  
Deep Water ◽  
Three Dimensional ◽  
Sediment Supply ◽  
Fine Grained ◽  
Basin Floor ◽  
Detachment Surface ◽  
Image Part

AbstractThree-dimensional (3D) seismic data reveal the complex interplay between the surface topography of a c. 4405 km3 mass transport deposit (MTD) and overlying sedimentary packages over approximately the last two million years. The data image part of the Pleistocene to recent shelf to slope to basin-floor Giant Foresets Formation in offshore western New Zealand. The MTD created substantive topographic relief and rugosity at the contemporaneous seabed, formed by the presence of a shallow basal detachment surface, and very large (up to 200 m high) intact slide blocks, respectively. Sediments were initially deflected away from high-relief MTD topography and confined in low areas. With time, the MTD was progressively healed by a series of broadly offset-stacked and increasingly unconfined packages comprised of many channel bodies and their distributary complexes. Positive topography formed by the channels and their distributary complexes further modified the seafloor and influenced the location of subsequent sediment deposition. Channel sinuosity increased over time, interpreted as the result of topographic healing and reduced seafloor gradients. The rate of sediment supply is likely to have been non-uniform, reflecting tectonic pulses across the region. Sediments were routed into deep water via slope-confined channels that originated shortly before emplacement of the MTD.

scholarly journals TB or not TB: banding in turbidite sandstones

2020 ◽  
Vol 90 (8) ◽  
pp. 821-842
Author(s):  
Christopher J. Stevenson ◽  
Jeff Peakall ◽  
David M. Hodgson ◽  
Daniel Bell ◽  
Aurélia Privat
Keyword(s):  
Flow Regime ◽  
Deep Water ◽  
Sedimentary Facies ◽  
Water Systems ◽  
Sedimentary Processes ◽  
Grain Sizes ◽  
Facies Associations ◽  
Flow Deceleration ◽  
Upper Stage ◽  
Low Amplitude

ABSTRACT Recognition and interpretation of sedimentary structures is fundamental to understanding sedimentary processes. Banded sandstones are an enigmatic sedimentary facies comprising alternating mud-rich (as matrix and/or mud clasts) and cleaner sand layers. The juxtaposition of hydrodynamically different grain sizes contradicts established models of cleaner-sand bedform development. Here, outcrop, subsurface core, and petrographic data from three deep-water systems, with well-constrained paleogeographic contexts, are used to describe the range of sedimentary textures, bedform morphologies, and facies associations, and to quantify the mud content of banding. Banding can occur in any part of a bed (base, middle, or top), but it typically overlies a structureless basal sandstone or mud-clast conglomerate lag, and is overlain by clean parallel-laminated sandstone and/or ripple cross-lamination. Banding morphology ranges from sub-parallel to bedforms that comprise low-angle laminae with discontinuous lenses of mudstone, or asymmetric bedforms comprising steeply dipping foresets that transition downstream into low-amplitude bedwaves, or steeply dipping ripple-like bedforms with heterolithic foresets. This style of banding is interpreted as a range of bedforms that form progressively in the upper-stage plane-bed flow regime via tractional reworking beneath mud-laden transitional plug flows. The balance of cohesive and turbulent forces, and the rate of flow deceleration (aggradation rate), govern the style of deposit. Banded sandstones and linked debrites are rarely found juxtaposed together in the same bed because they are distributed preferentially in proximal and distal settings, respectively. Understanding the origins of banding in turbidite sandstones, the conditions under which it forms, and its distribution across deep-water systems and relationship to linked debrites, is important for it to be used effectively as a tool to interpret the geological record.

Outcrop and Seismic Examples of Mass-Transport Deposits from a Late Miocene Deep-Water Succession, Taranaki Basin, New Zealand

2011 ◽  
pp. 311-348 ◽  
Author(s):  
PETER R. KING ◽  
BRADLEY R. ILG ◽  
MALCOLM ARNOT ◽  
GREG H. BROWNE ◽  
LORNA J. STRACHAN ◽  
...  
Keyword(s):  
New Zealand ◽  
Mass Transport ◽  
Deep Water ◽  
Late Miocene ◽  
Mass Transport Deposits

Lithostratigraphy of the Skoorsteenberg Formation (Ecca Group, Karoo Supergroup), South Africa

2017 ◽  
Vol 120 (3) ◽  
pp. 433-446
Author(s):  
H. de V. Wickens ◽  
D.I. Cole
Keyword(s):  
South Africa ◽  
Deep Water ◽  
Regional Distribution ◽  
Water Systems ◽  
Fine Grained ◽  
Karoo Basin ◽  
Porosity And Permeability ◽  
Basin Floor ◽  
Primary Porosity ◽  
Lower Slope

Abstract The Middle Permian Skoorsteenberg Formation is part of the Ecca Group (Karoo Supergroup) of South Africa. It is also known as the ‘Tanqua fan complex’ due to its origin as a deep-water sedimentation unit associated with a prograding deltaic system. The Skoorsteenberg Formation crops out over approximately 650 km2 along the western margin of the Main Karoo Basin. It thins out in a northerly and easterly direction and therefore has a limited extent with cut-off boundaries to the south and north. It is underlain by the Tierberg Formation and overlain by the Kookfontein Formation, the latter being limited to the regional distribution of the Skoorsteenberg Formation. The Skoorsteenberg Formation has a composite thickness of 400 m and comprises five individual sandstone packages, separated by shale units of similar thickness. The sandstones are very fine- to fine-grained, light greyish to bluish grey when fresh, poorly sorted and lack primary porosity and permeability. The Tanqua fan complex is regarded as one of the world’s best examples of an ancient basin floor to slope fan complex associated with a fluvially dominated deltaic system. It has served as analogue for many deep-water systems around the world and continues to be a most sought after “open-air laboratory” for studying the nature of fine-grained, deep-water sedimentation. The fan systems are essentially tectonically undeformed, outstandingly well exposed and contain an inexhaustible amount of information on the deep-water architecture of lower slope to basin floor turbidite deposits.

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