scholarly journals Interactions between deep-water gravity flows and active salt tectonics

2021 ◽  
Vol 91 (1) ◽  
pp. 34-65
Author(s):  
Zoë A. Cumberpatch ◽  
Ian A. Kane ◽  
Euan L. Soutter ◽  
David M. Hodgson ◽  
Christopher A-L. Jackson ◽  
...  
Keyword(s):  
Deep Water ◽  
Seafloor Topography ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Gravity Flows ◽  
Stratigraphic Architecture ◽  
Sediment Deformation ◽  
Depositional Systems ◽  
Partial Confinement ◽  
Depositional Architecture

ABSTRACTBehavior of sediment gravity flows can be influenced by seafloor topography associated with salt structures; this can modify the depositional architecture of deep-water sedimentary systems. Typically, salt-influenced deep-water successions are poorly imaged in seismic reflection data, and exhumed systems are rare, hence the detailed sedimentology and stratigraphic architecture of these systems remains poorly understood.The exhumed Triassic (Keuper) Bakio and Guernica salt bodies in the Basque–Cantabrian Basin, Spain, were active during deep-water sedimentation. The salt diapirs grew reactively, then passively, during the Aptian–Albian, and are flanked by deep-water carbonate (Aptian–earliest Albian Urgonian Group) and siliciclastic (middle Albian–Cenomanian Black Flysch Group) successions. The study compares the depositional systems in two salt-influenced minibasins, confined (Sollube basin) and partially confined (Jata basin) by actively growing salt diapirs, comparable to salt-influenced minibasins in the subsurface. The presence of a well-exposed halokinetic sequence, with progressive rotation of bedding, beds that pinch out towards topography, soft-sediment deformation, variable paleocurrents, and intercalated debrites indicate that salt grew during deposition. Overall, the Black Flysch Group coarsens and thickens upwards in response to regional axial progradation, which is modulated by laterally derived debrites from halokinetic slopes. The variation in type and number of debrites in the Sollube and Jata basins indicates that the basins had different tectonostratigraphic histories despite their proximity. In the Sollube basin, the routing systems were confined between the two salt structures, eventually depositing amalgamated sandstones in the basin axis. Different facies and architectures are observed in the Jata basin due to partial confinement.Exposed minibasins are individualized, and facies vary both spatially and temporally in agreement with observations from subsurface salt-influenced basins. Salt-related, active topography and the degree of confinement are shown to be important modifiers of depositional systems, resulting in facies variability, remobilization of deposits, and channelization of flows. The findings are directly applicable to the exploration and development of subsurface energy reservoirs in salt basins globally, enabling better prediction of depositional architecture in areas where seismic imaging is challenging.

EVOLUTION AND MORPHOLOGY OF RAFTED BLOCKS IN AN ANCIENT DEEPWATER MASS TRANSPORT COMPLEX (EXMOUTH PLATEAU, OFFSHORE NW AUSTRALIA)

2020 ◽  
pp. 1-67 ◽  
Author(s):  
Ovie Emmanuel Eruteya ◽  
Yakufu Niyazi ◽  
Kamaldeen Olakunle Omosanya ◽  
Daniel Ierodiaconou ◽  
Andrea Moscariello
Keyword(s):  
Mass Transport ◽  
Deep Water ◽  
High Amplitude ◽  
3D Seismic ◽  
Complex Flow ◽  
Seismic Reflection Data ◽  
Exmouth Plateau ◽  
Reflection Data ◽  
Transport Complex ◽  
Nw Australia

Submarine mass wasting plays a fundamental role in transporting substantial volumes of sediments basinward including gigantic slide blocks. However, the understanding of processes involved in block generation and their associated deformation until flow arrest remains limited, especially in data-starved deep-water settings. Here a 2D and 3D seismic reflection data from the Exmouth Plateau, offshore NW Australia is used to investigate the architecture of large blocks preserved within an ancient mass transport complex (MTC) and their interaction with the basal shear surface (BSS). The evolution of the investigated MTC (MTC-BDF) is related to instability along the flanks of an underlying bifurcative Miocene canyon. MTC-BDF spans ∼75 km by ∼35 km containing at least 32 well-imaged blocks (within the 3D seismic coverage) encapsulated in a well-deformed debrite background. These carbonate blocks interpreted as rafted blocks have lengths ranging from 0.48 km to 3.40 km with thicknesses reaching up to 165 m. Interestingly, the blocks are more abundant in a region characterized by moderate-high amplitude debrites. Erosional morphologies encompassing a unique groove and other circular to irregular-shaped depressions mapped along the BSS provide evidence for the erosive nature of the flow. The origin of the groove is related transported blocks gouging the BSS. Importantly, intra block deformations recorded within these blocks as fault and fold systems suggest a complex flow regime within MTC-BDF, with the deformations arising either during block translation or also possibly upon the arrest of the failed mass in interaction with bathymetric elements. Our findings suggest inherent deformations within these blocks may serve as high-permeability conduits with implications for deep-water drilling operations within this segment of the Exmouth Plateau and elsewhere in other hydrocarbon-rich deep-water settings.

scholarly journals Extrusion dynamics of deep-water volcanoes

2019 ◽  
Author(s):  
Qiliang Sun ◽  
Christopher A.-L. Jackson ◽  
Craig Magee ◽  
Samuel J. Mitchell ◽  
Xinong Xie
Keyword(s):  
Deep Water ◽  
Seismic Reflection ◽  
Minor Component ◽  
Lava Flows ◽  
Lava Tubes ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Seafloor Sediments ◽  
A Minor ◽  
Seabed Sediments

Abstract. Submarine volcanism accounts for c. 75 % of the Earth's volcanic activity. Yet difficulties with imaging their exteriors and interiors mean the extrusion dynamics and erupted volumes of deep-water volcanoes remain poorly understood. Here, we use high-resolution 3-D seismic reflection data to examine the external and internal geometry, and extrusion dynamics of two Late Miocene-Quaternary, deep-water (> 2 km emplacement depth) volcanoes buried beneath 55–330 m of sedimentary strata in the South China Sea. The volcanoes have crater-like basal contacts, which truncate underlying strata, and erupted lava flows that feed lobate lava fans. The lava flows are > 9 km long and contain lava tubes that have rugged basal contacts defined by ~ 90 ± 23 m high erosional ramps. We suggest the lava flows eroded down into and were emplaced at shallow sub-surface depths within wet, unconsolidated, near-seafloor sediments. Extrusion dynamics were likely controlled by low magma viscosities, high hydrostatic pressures, and soft, near-seabed sediments, which collectively are characteristic of deep-water environments. Because the lava flows and volcanic edifices are imaged in 3D, we calculate the lava flows account for 50–97 % of the total erupted volume. Our results indicate deep-water volcanic edifices may thus form a minor component (~ 3–50 %) of the extrusive system, and that accurate estimates of erupted volume requires knowledge of the basal surface of genetically related lava flows. We conclude that 3D seismic reflection data is a powerful tool for constraining the geometry and extrusion dynamics of buried, deep-water volcanic features; such data should be used to image and quantify extrusion dynamics of modern deep-water volcanoes.

Characteristics and generation mechanism of gullies and mega-pockmarks in the Zhongjiannan Basin, western South China Sea

2017 ◽  
Vol 5 (3) ◽  
pp. SM49-SM59 ◽  
Author(s):  
Minghui Geng ◽  
Haibin Song ◽  
Yongxian Guan ◽  
Jiang Xin Chen ◽  
Yang Bai
Keyword(s):  
Fluid Flow ◽  
South China Sea ◽  
South China ◽  
Generation Mechanism ◽  
Seismic Reflection Data ◽  
China Sea ◽  
Reflection Data ◽  
Gravity Flows ◽  
Close Relationship ◽  
Multichannel Seismic Reflection Data

The paleoceanography and deep-water circulation process of the South China Sea (SCS) is still poorly understood. We have evaluated multibeam bathymetry and multichannel seismic reflection data acquired by Guangzhou Marine Geological Survey in recent years, and we investigate the characteristics, distribution, and generation mechanism of submarine seabed gullies and mega-pockmarks in the northern Zhongjiannan Basin of the SCS. Our data reveal that there are northwest–southeast-trending gullies and randomly or linearly arraying mega-pockmarks in the northern depression of the Zhongjiannan Basin. Gullies are 1 km or more in width and tens of kilometers in length. The long-axis diameter for the largest mega-pockmarks can reach up to 4293 m. The mega-pockmarks found in the west block of the northern depression are the manifestation of focused fluid flow migrating along shallow inclined faults induced by slumps that reached the seabed. Gullies are trending southeast and perpendicular to the contours of the continental slope, suggesting that gravity flows have played an important role in the evolution of gullies. Our data demonstrate that the gullies have a close relationship with mega-pockmarks, and that they were formed through the interaction of intense focused fluid flow and gravity flows. The pockmarks formed first, subsequently growing in size and number under the effect of subsurface fluid flows. The southeastward moving gravity flow caused discrete pockmarks to coalesce and form immature gullies. After being fully converged, gullies finally become smooth-bottomed and matured. Because gullies and mega-pockmarks are the manifestation of the geologic process of fluid escape at the seabed, they should be taken into account when assessing the potential for gas hydrates and seafloor instability.

The influence of stratigraphic architecture on seismic response: Reflectivity modeling of outcropping deepwater channel units

2018 ◽  
Vol 6 (3) ◽  
pp. T783-T808 ◽  
Author(s):  
Erin A. L. Pemberton ◽  
Lisa Stright ◽  
Sean Fletcher ◽  
Stephen M. Hubbard
Keyword(s):  
Aspect Ratio ◽  
Seismic Reflection ◽  
Reservoir Prediction ◽  
Seismic Reflection Data ◽  
Architectural Elements ◽  
Reflection Data ◽  
Sediment Routing ◽  
Stratigraphic Architecture ◽  
Seismic Reflections ◽  
Confined Channel

The size, shape, stacking patterns, and internal architecture of deepwater deposits control reservoir fluid flow connectivity. Predicting deepwater stratigraphic architecture as a function of position along a deepwater slope from seismic-reflection data is critical for successful hydrocarbon exploration and development projects. Stratigraphic architecture from confined and weakly confined segments of a deepwater sediment-routing system is analyzed in outcrop from the Tres Pasos Formation (Upper Cretaceous), southern Chile. Outcrop observations are the basis of two geocellular models: confined channel deposits at Laguna Figueroa and weakly confined channel and scour deposits at Arroyo Picana. Key stratigraphic surfaces and facies relationships observed in outcrop are forward seismic modeled at high to low resolution to bridge the gap in subseismic scale interpretation of deepwater reservoirs and demonstrate challenges associated with identification of varied reservoir architecture. The outcrop-constrained geometry of architectural elements, their stacking arrangement, and the varied internal distribution of facies each impart a strong influence on seismic reflectivity. Key outcomes from the analysis include (1) stratigraphic architecture transitions down-paleoslope from vertically aligned low-aspect-ratio channel elements to a more weakly confined depocenter characterized by a breadth of laterally offset low- and high-aspect-ratio channel and scour elements. Seismic reflections, down to 30 Hz frequencies, record aspects of these stratigraphic changes. (2) Key seismic reflections are often comprised of multiple outcrop-constrained stratigraphic surfaces. Tuning effects result in composite seismic surfaces that are vertically offset from the known position of sedimentary units; this hinders accurate interpretation of stratigraphic surfaces from seismic-reflection data. This is particularly problematic in the weakly confined system in which shifted stratigraphic surfaces, which bound deposits characterized by numerous similar architectural elements, can alter the interpretability of sandstone connectivity within and across zones. Furthermore, misinterpretation of surfaces is problematic when they are flow barriers draped with debris flows, slumps/slides, or thin-bedded turbidites. (3) Tuning effects also impart significant control on volume-based interpretations from seismic data. In particular, calculations of gross rock volume from seismic reflection data that do not consider the tuning or architectural element stacking pattern can overestimate actual volumes by 10%–50%, with implications for reservoir prediction and hydrocarbon volume estimation.

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

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.

scholarly journals Active faulting controls bedform development on a deep-water fan

Geology ◽  
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.

Benthic foraminiferal zonation in deep-water carbonate platform margin environments, northern Little Bahama Bank

1988 ◽  
Vol 62 (01) ◽  
pp. 1-8 ◽  
Author(s):  
Ronald E. Martin
Keyword(s):  
Deep Water ◽  
Benthic Foraminifera ◽  
Carbonate Platform ◽  
Sedimentary Facies ◽  
Depositional Environments ◽  
Near Surface ◽  
Sediment Gravity Flows ◽  
Gravity Flows ◽  
Platform Margin ◽  
Water Carbonate

The utility of benthic foraminifera in bathymetric interpretation of clastic depositional environments is well established. In contrast, bathymetric distribution of benthic foraminifera in deep-water carbonate environments has been largely neglected. Approximately 260 species and morphotypes of benthic foraminifera were identified from 12 piston core tops and grab samples collected along two traverses 25 km apart across the northern windward margin of Little Bahama Bank at depths of 275-1,135 m. Certain species and operational taxonomic groups of benthic foraminifera correspond to major near-surface sedimentary facies of the windward margin of Little Bahama Bank and serve as reliable depth indicators. Globocassidulina subglobosa, Cibicides rugosus, and Cibicides wuellerstorfi are all reliable depth indicators, being most abundant at depths >1,000 m, and are found in lower slope periplatform aprons, which are primarily comprised of sediment gravity flows. Reef-dwelling peneroplids and soritids (suborder Miliolina) and rotaliines (suborder Rotaliina) are most abundant at depths <300 m, reflecting downslope bottom transport in proximity to bank-margin reefs. Small miliolines, rosalinids, and discorbids are abundant in periplatform ooze at depths <300 m and are winnowed from the carbonate platform. Increased variation in assemblage diversity below 900 m reflects mixing of shallow- and deep-water species by sediment gravity flows.

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