How do tectonics influence the initiation and evolution of submarine canyons A case study from the Otway Basin, SE Australia

The architecture of canyon-fills can provide a valuable record of the link between tectonics, sedimentation, and depositional processes in submarine settings. We integrate 3D and 2D seismic reflection data to investigate the dominant tectonics and sedimentary processes involved in the formation of two deeply buried (c. 500 m below seafloor), and large (c. 3-6 km wide, >35 km long) Late Miocene submarine canyons. We found the plate tectonic-scale events (i.e. continental breakup and shortening) have a first-order influence on the submarine canyon initiation and evolution. Initially, the Late Cretaceous (c. 65 Ma) separation of Australia and Antarctica resulted in extensional fault systems, which then formed stair-shaped paleo-seabed. This inherited seabed topography allowed gravity-driven processes (i.e. turbidity currents and mass-transport complexes) to occur. Subsequently, the Late Miocene (c. 5 Ma) collision of Australia and Eurasia, and the resulting uplift and exhumation, have resulted in a prominent unconformity surface that coincides with the base of the canyons. We suggest that the Late Miocene intensive tectonics and associated seismicity have resulted in instability in the upper slope that consequently gave rise to emplacement of MTCs, initiating the canyons formation. Therefore, we indicate that regional tectonics play a key role in the initiation and development of submarine canyons.

Download Full-text

COOL-WATER CARBONATE FACIES PATTERNS AND DIAGENESIS-THE KEY TO THE GIPPSLAND BASIN 'VELOCITY PROBLEM'

The APPEA Journal ◽

10.1071/aj97007 ◽

1998 ◽

Vol 38 (1) ◽

pp. 137 ◽

Cited By ~ 8

Author(s):

D.A. Feary ◽

T.S. Loutit

Keyword(s):

Submarine Canyon ◽

Velocity Variation ◽

Carbonate Facies ◽

Seismic Attribute ◽

Seismic Reflection Data ◽

Cool Water ◽

Depositional Processes ◽

Attribute Analysis ◽

Gippsland Basin ◽

Water Carbonate

Throughout much of the exploration history of the offshore Gippsland Basin it has been difficult to achieve acceptable accuracy or precision for time-depth conversions beneath the stratigraphically and sonically complex Seaspray Group, overlying exploration targets within the hydrocarbon-rich Latrobe Group. A regional seismic stratigraphic and seismic attribute analysis of the Oligocene-Recent Seaspray Group has been carried out as the first step towards resolving this long-standing Gippsland Basin 'velocity problem'.High-resolution 2D seismic reflection data and downhole logs were used to determine the depositional history and sequence characteristics of the Seaspray Group. This analysis was based on the premise that velocity variation must be related to, or controlled by, the nature and distribution of the dominantly cool-water carbonate facies of the Seaspray Group, and that solution of the velocity problem must be based on understanding the particular depositional and geochemical characteristics of cool-water carbonates.Detailed seismic stratigraphic analysis of the G92A dataset shows that the 16 unconformity-bounded seismic sequences within the Seaspray Group form four mega-sequences, each separated by major erosional (channel-cutting) events, with sequences reflecting variable sediment inputs from northeasterly and southwesterly sources. Seaspray Group characteristics result from interaction of complex depositional and post-depositional processes, including river incision, submarine canyon erosion, slumping, subaerial exposure, karstification, and subsurface diagenesis and erosion. Seismic attribute analysis records the variability of diagenesis and shows that diagenetic effects are predominantly concentrated along sequence boundaries, sometimes to significant depths below the sequence boundary.Results to date indicate that application of a velocity model based on this new interpretation will enable improved precision of depth estimates to the top Latrobe Group unconformity to less than five per cent.

Download Full-text

The Ogooue Fan (offshore Gabon): a modern example of deep-sea fan on a complex slope profile

Solid Earth ◽

10.5194/se-10-851-2019 ◽

2019 ◽

Vol 10 (3) ◽

pp. 851-869 ◽

Cited By ~ 1

Author(s):

Salomé Mignard ◽

Thierry Mulder ◽

Philippe Martinez ◽

Thierry Garlan

Keyword(s):

Deep Sea ◽

Sedimentary Facies ◽

Turbidity Currents ◽

Slope Gradient ◽

Seismic Reflection Data ◽

Fine Grained ◽

Reflection Data ◽

Deposition Processes ◽

Sea Fan ◽

The Impact

Abstract. The effects of changes in slope gradient on deposition processes and architecture have been investigated in different deep-sea systems both in modern and ancient environments. However, the impact of subtle gradient changes (< 0.3∘) on sedimentary processes along deep-sea fans still needs to be clarified. The Ogooue Fan, located in the northeastern part of the Gulf of Guinea, extends over more than 550 km westwards of the Gabonese shelf and passes through the Cameroon volcanic line. Here, we present the first study of acoustic data (multibeam echosounder and 3.5 kHz, very high-resolution seismic data) and piston cores covering the deep-sea part of this West African system. This study documents the architecture and sedimentary facies distribution along the fan. Detailed mapping of near-seafloor seismic-reflection data reveals the influence of subtle slope gradient changes (< 0.2∘) along the fan morphology. The overall system corresponds to a well-developed deep-sea fan, fed by the Ogooue River sedimentary load, with tributary canyons, distributary channel–levee complexes and lobe elements. However, variations in the slope gradient due to inherited salt-related structures and the presence of several seamounts, including volcanic islands, result in a topographically complex slope profile including several ramps and steps. In particular, turbidity currents derived from the Gabonese shelf deposit cross several interconnected intra-slope basins located on the low gradient segments of the margin (< 0.3∘). On a higher gradient segment of the slope (0.6∘), a large mid-system valley developed connecting an intermediate sedimentary basin to the more distal lobe area. Distribution and thickness of turbidite sands is highly variable along the system. However, turbidite sands are preferentially deposited on the floor of the channel and the most proximal depositional areas. Core description indicates that the upper parts of the turbidity flows, mainly composed of fine-grained sediments, are found in the most distal depocenters.

Download Full-text

Entrainment and abrasion of megaclasts during submarine landsliding and their impact on flow behaviour

Geological Society London Special Publications ◽

10.1144/sp477.26 ◽

2018 ◽

Vol 477 (1) ◽

pp. 223-240 ◽

Cited By ~ 4

Author(s):

D. M. Hodgson ◽

H. L. Brooks ◽

A. Ortiz-Karpf ◽

Y. Spychala ◽

D. R. Lee ◽

...

Keyword(s):

Seismic Reflection ◽

Three Dimensional ◽

Submarine Landslides ◽

Seismic Reflection Data ◽

Karoo Basin ◽

Reflection Data ◽

Seabed Topography ◽

Flow Evolution ◽

Basal Shear ◽

Process Product

AbstractMany mass transport complexes (MTCs) contain up to kilometre-scale (mega)clasts encased in a debritic matrix. Although many megaclasts are sourced from the headwall areas, the irregular basal shear surfaces of many MTCs indicate that megaclast entrainment during the passage of flows into the deeper basin is also common. However, the mechanisms responsible for the entrainment of large blocks of substrate, and their influence on the longitudinal behaviour of the associated flows, have not been widely considered. We present examples of megaclasts from exhumed MTCs (the Neuquén Basin, Argentina and the Karoo Basin, South Africa) and MTCs imaged in three-dimensional seismic reflection data (Magdalena Fan, offshore Colombia and Santos Basin, offshore Brazil) to investigate these process–product interactions. We show that highly sheared basal surfaces are well developed in distal locations, sometimes extending beyond their associated deposit. This points to deformation and weakening of the substrate ahead of the flow, suggesting that preconditioning of the substrate by distributed shear ahead of, and to the side of, a mass flow could result in the entrainment of large fragments. An improved understanding of the interactions between flow evolution, seabed topography, and the entrainment and abrasion of megaclasts will help to refine estimates of run-out distances, and therefore the geohazard potential of submarine landslides.

Download Full-text

Basin subsidence and Miocene/Pliocene sedimentary change in the Browse Basin, NW Australia

10.5194/egusphere-egu2020-21627 ◽

2020 ◽

Author(s):

Sebastian Thronberens ◽

Stefan Back ◽

Lars Reuning ◽

Julien Bourget

Keyword(s):

Late Miocene ◽

Seismic Reflection ◽

Shelf Edge ◽

Sr Isotope ◽

Borehole Data ◽

Seismic Reflection Data ◽

X Ray ◽

Reflection Data ◽

Basin Subsidence ◽

Isotope Dating

<p>The upper Miocene to Pliocene interval of the Browse Basin on the Australian North West Shelf (NWS) records a significant paleo-environmental change in its sedimentary record concerning the decay of middle to late Miocene tropical reefs. Seismic observations towards the Pliocene show a clear landward migration of carbonate build-ups in the eastern part of the basin, and very high subsidence rates seem to have outpaced most reef growth in distal shelf-edge positions. Nevertheless, the Scott Reef and the Seringapatam Reef were able to withstand shelf-edge drowning, which indicates a significant contribution of inversion-related uplift for reef survival. The contribution of basin subsidence as a driving factor for this reef decay and survival is still discussed and has not been studied in detail. This study provides an estimate for the laterally and through time changing late Miocene/Pliocene subsidence pattern. A 3D paleo-environmental reconstruction was generated by 3D quantitative backstripping, integrating 3D paleo-waterdepth information derived from seismic-based depositional system interpretation. The base of this analysis is a giant 2D and 3D seismic-reflection data set (>130.000 km&#178;) integrated with borehole data (logs, cores, cuttings), new Sr-isotope dating, X-ray diffractometry (XRD) and microfacies analyses, supporting paleo-bathymetric correction and ties to global sea-level data. The seismic-reflection data is covering a study area extending over 130.000 km&#178; and is supported by industry borehole data (logs, cores, and cuttings), SR-Isotope dating, X-Ray diffractometry (XRD) and microfacies analysis.</p>

Download Full-text

Transport and accumulation of plastic litter in submarine canyons—The role of gravity flows

Geology ◽

10.1130/g48536.1 ◽

2021 ◽

Author(s):

Guangfa Zhong ◽

Xiaotong Peng

Keyword(s):

Submarine Canyon ◽

Turbidity Currents ◽

Size Distributions ◽

Submarine Canyons ◽

Seabed Sediment ◽

Gravity Flows ◽

Grain Size Distributions ◽

Manned Submersible ◽

Bimodal Grain Size

Manned submersible dives discovered plastic litter accumulations in a submarine canyon located in the northwestern South China Sea, ~150 km from the nearest coast. These plastic-dominated litter accumulations were mostly concentrated in two large scours in the steeper middle reach of the canyon. Plastic particles and fragments generally occurred on the upstreamfacing sides of large boulders and other topographic obstacles, indicating obstruction during down-valley transportation. Most of the litter accumulations were distributed in the up-valley dipping slopes downstream of the scour centers. This pattern is tentatively linked to turbidity currents, which accelerated down the steep upstream slopes of the scours and underwent a hydraulic jump toward the scour centers before decelerating on the upstream-facing flank. Associated seabed sediment consisted of clayey and sandy silts, with unimodal or bimodal grain-size distributions, which are typical for turbidites. The focused distribution of the litter accumulations is therefore linked to turbidity currents that episodically flush the canyon. Our findings provide evidence that litter dispersion in the deep sea may initially be governed by gravity flows, and that turbidity currents efficiently transfer plastic litter to the deeper ocean floor.

Download Full-text

Quartz arenites of the Cambro-Ordovician Kamouraska Formation, Quebec Appalachians, Canada: I. Deep-water depositional processes in a continental-slope environment

Canadian Journal of Earth Sciences ◽

10.1139/e11-005 ◽

2011 ◽

Vol 48 (8) ◽

pp. 1209-1231 ◽

Cited By ~ 3

Author(s):

Pierre Malhame ◽

Reinhard Hesse

Keyword(s):

Continental Slope ◽

Deep Water ◽

Submarine Canyon ◽

Turbidity Currents ◽

Lawrence Estuary ◽

Depositional Processes ◽

Iapetus Ocean ◽

Quartz Arenite ◽

Exposed Part ◽

Polymictic Conglomerate

The Kamouraska Formation is an uppermost Cambrian – lowermost Ordovician quartz-arenite-dominated unit of controversial origin deposited on the southeastern slope of Laurentia bordering the Iapetus Ocean. It is exposed in the Quebec Appalachians on the south shore of the St. Lawrence Estuary. The formation consists of basal polymictic conglomerate and overlying massive sheet-like quartz arenite. The conglomerate beds are reversely and reversely to normally graded. The quartz arenite beds are generally massive, although they may show coarse-tail grading. Beds containing full or partial Bouma sequences are rare. Paleoflow directions from ripple-cross lamination, ripple marks on bed surfaces, and sole marks point towards southeast, south, and southwest. The clastic sediments of the Kamouraska were transported into the deep sea by sediment gravity flows that evolved from hyperconcentrated to concentrated density flows, and then to turbidity currents. The depositional environment is interpreted to have been a southwest-trending meandering submarine canyon. The exposed part of the canyon deposits is slightly oblique to the strike of slope. If correct, our interpretation establishes the preservation of continental-slope deposits in more distal deep-water siliciclastic sedimentary rocks of the Taconian orogen in Quebec, which traditionally have been interpreted as submarine-fan and (or) basin-plain deposits. The orientation of a canyon near parallel-to strike of the slope may have been controlled by syn-depositional growth faults. The coarsest hyperconcentrated flows, which deposited the conglomerate, were restricted to the deepest parts of the canyon during its early stages of development, whereas the concentrated density flows that deposited the massive quartz-arenite beds covered a wider area.

Download Full-text

Ultra-slow throw rates of polygonal fault systems

Geology ◽

10.1130/g47221.1 ◽

2020 ◽

Vol 48 (5) ◽

pp. 473-477

Author(s):

James J. King ◽

Joe A. Cartwright

Keyword(s):

Three Dimensional ◽

Volumetric Strain ◽

Time Frame ◽

Normal Faults ◽

Seismic Reflection Data ◽

Fine Grained ◽

Fault Systems ◽

Reflection Data ◽

Gravity Driven ◽

Polygonal Fault

Abstract Polygonal fault systems (PFSs) are an enigmatic class of small nontectonic extensional faults. PFSs are predominantly hosted in fine-grained sedimentary tiers and are prevalent along many continental margin basins. The genesis of PFSs is widely debated, and little is known about the time frame for polygonal fault growth. We present the first measurements of throw rates for polygonal faults by measuring the vertical offset of seven age-calibrated horizons mapped using three-dimensional seismic reflection data from the Norwegian Sea. Individual polygonal faults exhibit a range of throw rate profiles through time, ranging from near linear to singly or multiply stepped. The stepped profiles have short-term throw rates ranging from 0 to 18 m/m.y. Time-averaged throw rates of 180 polygonal faults over the entire 2.61–0 Ma interval are normally distributed and range between 1.4 and 10.9 m/m.y. We convert our PFS throw rates to displacement rates and compare these to published displacement rates for gravity-driven and tectonic normal faults. We find that the displacement rates of polygonal faults mark the lower limit of a continuous spectrum of extensional fault displacement rates; they are as much as two orders of magnitude slower than those of gravity-driven faults, and as much as three orders of magnitude slower than those of the fastest-growing tectonic faults. We attribute the ultra-slow kinematic behavior to the nontectonic nature of polygonal faults, where throw accumulates primarily through dewatering of the largely fine-grained sediments composing the host layers for the PFSs, and through differential volumetric strain between the fault footwalls and hanging walls.

Download Full-text

Plio-Pleistocene glacial history of the Melville Bugt Ice Stream

10.5194/egusphere-egu2020-19312 ◽

2020 ◽

Author(s):

Andrew Newton ◽

David Cox ◽

Mads Huuse ◽

Paul Knutz

Keyword(s):

Seismic Reflection ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Middle Pleistocene ◽

Seismic Reflection Data ◽

Baffin Bay ◽

Reflection Data ◽

West Greenland Current ◽

Hyperpycnal Flows ◽

Gravity Driven

<p>In this work we use high-resolution seismic reflection surveys collected across the northeast Baffin Bay region to investigate the glacigenic Melville Bugt Trough Mouth Fan (MB-TMF). The MB-TMF stratigraphy is characterised by over 100 km of progradation since ~2.7 Ma and the heterogeneous truncation or subsidence of topset strata. Variation in topset character is thought to relate to the waxing and waning of the northwest sector of the Greenland Ice Sheet across the shelf since ~2.7 Ma. 3D seismic reflection data reveal the preservation of multiple sets of mega-scale glacial lineations, suggesting that grounded ice extended across the shelf a number of times since the onset of the Middle Pleistocene Transition. Seismic geomorphology and facies analysis of the prograding clinoforms show repeated observations of debrites and gully systems. These features, when considered with other evidence of adjacent glacial landforms and strata, are taken to infer gravity-driven processes and the presence of meltwater-related hyperpycnal flows in areas proximal to the ice sheet on the outer shelf. Bottomset contourites at the base of the continental slope also provide insights into the evolution of the West Greenland Current in Baffin Bay through the Pleistocene, with deposition estimated to have started in the latest Calabrian, based on the current age model. Regional stratigraphic mapping shows that the MB-TMF can be summarised into four stages that were primarily controlled by variations in ice sheet erosion patterns, topographic forcing of ice flow, and changes in accommodation that are related to glacigenic deposition and tectonic subsidence.&#160;</p>

Download Full-text

The role of mass-transport complexes (MTCs) in the initiation and evolution of submarine canyons

10.31223/x58k7d ◽

2021 ◽

Author(s):

Nan Wu ◽

Harya Nugraha ◽

Fa Zhong ◽

Michael Steventon

Keyword(s):

Mass Transport ◽

Continental Shelf ◽

Failure Mechanism ◽

Fluvial Systems ◽

Offshore Area ◽

Seismic Reflection Data ◽

Reflection Data ◽

Gravity Flows ◽

Flow Convergence ◽

Gravity Driven

The offshore area of the Otway Basin, located within the SE continental margin of Australia, is dominated by a multibranched canyon system where submarine mass-transport complexes (MTCs) are widely distributed. We integrate high-resolution multi-beam bathymetric and seismic reflection data to investigate the importance of regionally distributed MTCs in dictating the evolution of canyon systems. We interpret three regionally distributed MTCs that fail retrogressively and affect almost 70% of the study area. Within the MTCs, we observed seven canyons that initiated from the continental shelf edge and extended to the abyssal plain. Although these canyons share common regional tectonics and oceanography, the scales, morphology, and distribution are distinctly different. This is devoted to the presence of failure-related scarps (i.e. headwall and sidewall scarps) that control the initiation and formation of the canyons. The retrogressive failure mechanisms of MTCs have created a series of the headwall and lateral scarps on the continental shelf and slope regions. In the continental shelf, where terrestrial input (i.e. fluvial systems) is absent, the origin of the canyons is related to the local failure events and the contour current activities occurring near the pre-existing, massive headwall scarps (c. 120 m high, 3km long). The occurrence of these local failures has provided the necessary sediment input for subsequent gravity-driven, downslope sediment flows. In the continental slope region, the widespread scarps can capture gravity flows initiated from the continental shelf, developing an area of flow convergence, which greatly widens and deepens the canyon system. The gradual diversion and convergence through MTCs related scarps have facilitated the canyon confluence process, which has fundamentally changed the canyoning process. Thus, we conclude that the retrogressive failure mechanism of MTCs has a direct contribution to the initiation, distribution, and evolution of the canyons, especially in areas where fluvial input is missing. Moreover, the retrogressive failure mechanism is responsible for the canyon deepening and confluence process, which can greatly facilitate the delivery of sediment into deep oceans.

Download Full-text

Active faulting controls bedform development on a deep-water fan

Geology ◽

10.1130/g49206.1 ◽

2021 ◽

Author(s):

Vittorio Maselli ◽

Aaron Micallef ◽

Alexandre Normandeau ◽

Davide Oppo ◽

David Iacopini ◽

...

Keyword(s):

Flow Velocity ◽

Deep Water ◽

Eastern Mediterranean ◽

Hanging Wall ◽

Normal Fault ◽

Turbidity Currents ◽

Seismic Reflection Data ◽

Reflection Data ◽

Levant Basin ◽

Seismic Scale

Tectonically controlled topography influences deep-water sedimentary systems. Using 3-D seismic reflection data from the Levant Basin, eastern Mediterranean Sea, we investigate the spatial and temporal evolution of bedforms on a deep-water fan cut by an active normal fault. In the footwall, the fan comprises cyclic steps and antidunes along its axial and external portions, respectively, which we interpret to result from the spatial variation in flow velocity due to the loss of confinement at the canyon mouth. Conversely, in the hanging wall, the seafloor is nearly featureless at seismic scale. Numerical modeling of turbidity currents shows that the fault triggers a hydraulic jump that suppresses the flow velocity downstream, which thus explains the lack of visible bedforms basinward. This study shows that the topography generated by active normal faulting controls the downslope evolution of turbidity currents and the associated bedforms and that seafloor geomorphology can be used to evince syn-tectonic deposition.

Download Full-text