Miramontes, Elda
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Item-typ:Veröffentlichung, Incision of Submarine Channels Over Pockmark Trains in the South China SeaThe genesis of submarine channels is often controlled by gravity flows, but channels can also be formed by oceanographic processes. Using multibeam bathymetry and two-dimensional seismic data from the western South China Sea, this study reveals how pockmarks can ultimately form channels under the effect of bottom currents and gravity-driven sedimentary processes. We demonstrate that alongslope and across-slope channels were initiated by pockmark trains on the seafloor. Discrete pockmarks were elongated due to the erosion of gravity-driven sedimentary processes and bottom currents, and later coalesced to form immature channels with irregular thalwegs. These gradually evolved into mature channels with continuous overbanks and smooth thalwegs. Submarine channel evolution was significantly influenced by seafloor topography since the Late Miocene. The evolutionary model documented here is a key to understanding how channels are formed in deep-water environments.Wissenschaftlicher ArtikelBand:48Heft:e2021GL092861179 195 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Sequential bedform development in mixed turbidite–contourite systems: An example from the Cosmonaut Sea, East Antarctica(Elsevier, 2022-08-01); ; ; ; Mixed turbidite–contourite depositional systems are commonly found on continental margins, but their bedforms and associated sedimentary processes have not been studied in depth. In this work, we used multibeam echo-sounder, sub-bottom profiling, and multichannel seismic data from the continental rise of the Cosmonaut Sea, East Antarctica, to (1) identify primary bedforms in a combined-current (i.e., turbidity current + contour current) channel–levee system and (2) infer bedform-associated sedimentary processes. Within turbidite channels and on adjacent levees and distal overbank deposits, scours, furrows, and sediment waves of varying dimensions and trends were identified. These bedforms are interpreted to have formed in two steps, which have been likely repeated over and over again through time. First, scours and sediment waves within the channels were formed by turbidity currents, while sediment waves on adjacent levees were likely formed by synchronous interactions between overspilled unconfined turbidity currents and the westward Antarctic Bottom Water (AABW) contour current. Second, after waning of the episodic turbidity currents, AABW flow created a field of erosional furrows on a distal overbank, with these furrows truncating the large field of sediment waves earlier generated by the combined flow of interacting currents. Bedform locations, orientations, and truncating relationships are key for identifying the likely origins of mixed-system bedforms.Wissenschaftlicher ArtikelBand:410161 66 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, The impacts of profile concavity on turbidite deposits: Insights from the submarine canyons on global continental margins(2024-03-13); ; ; ; Submarine canyons are primary conduits for turbidity currents transporting terrestrial sediments, nutrients, pollutants and organic carbon to the deep sea. The concavity in the longitudinal profile of these canyons (i.e. the downstream flattening rate along the profiles) influences the transport processes and results in variations in turbidite thickness, impacting the transfer and burial of particles. To better understand the controlling mechanisms of canyon concavity on the distribution of turbidite deposits, here we investigate the variation in sediment accumulation as a function of canyon concavity of 20 different modern submarine canyons, distributed on global continental margins. In order to effectively assess the isolated impact of the concavity of 20 different canyons, a series of two-dimensional, depth-resolved numerical simulations are conducted. Simulation results show that the highly concave profile (e.g. Surveyor and Horizon) tends to concentrate the turbidite deposits mainly at the slope break, while nearly straight profiles (e.g. Amazon and Congo) result in deposition focused at the canyon head. Moderately concave profiles with a smoother canyon floor (e.g. Norfolk-Washington and Mukluk) effectively facilitate the downstream transport of suspended sediments in turbidity currents. Furthermore, smooth and steep upper reaches of canyons commonly contribute to sediment bypass (i.e. Mukluk and Chirikof), while low slope angles lead to deposition at upper reaches (i.e. Bounty and Valencia). At lower reaches, the distribution of turbidite deposits is consistent with the occurrence of hydraulic jumps. Under the influence of different canyon concavities, three types of deposition patterns are inferred in this study, and verified by comparison with observed turbidite deposits on the modern or paleo-canyon floor. This study demonstrates a potential difference in sediment transport efficiency of submarine canyons with different concavities, which has potential consequences for sediment and organic carbon transport through submarine canyons.Wissenschaftlicher Artikel254 57 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Contourite and mixed turbidite-contourite systems in the Mozambique Channel (SW Indian Ocean): Link between geometry, sediment characteristics and modelled bottom currentsOceanic currents can profoundly reshape the seafloor and even modify the characteristics of turbidite systems. Multiple erosional and depositional features directly formed by bottom currents (i.e. contourites), as well as by the interaction between bottom currents and turbidity currents or turbidite systems (i.e. mixed turbidite-contourite systems) have been identified in the Mozambique Channel (SW Indian Ocean) in multibeam bathymetry, seismic reflection data, sub-bottom profiler images and sediment cores. In this study, we characterise the morphology, stacking pattern and sedimentary characteristics of these sedimentary systems and analysed the properties of bottom currents at these systems using a hydrodynamic numerical model. Modelled bottom currents are the highest at abraded surfaces and moats, but they also display a relatively high variability, suggesting that the observed erosion is not the result of a constant or persistent current but rather of episodes of intense circulation. Modelled bottom currents at contourite terraces are not significantly different from currents at related plastered drifts, where accumulation is enhanced. The formation of contourite terraces can thus not solely be explained by the mean oceanic circulation and eddies, implying that other processes such as internal waves may play a relevant role in their formation. Three different types of mixed turbidite-contourite systems were observed: one characterised by asymmetric channel-levee systems formed by the synchronous interaction of bottom currents and turbidity currents, one characterised by a phased interaction that resulted in the erosion of the channel flanks by bottom currents, and another one in which both synchronous and phased interaction played a relevant role in the evolution of the system. Finally, we propose a simplified classification of contourites that can be applied to any contourite system worldwide, and that comprises erosional and depositional features, including muddy and sandy contourite deposits.Wissenschaftlicher Artikel146 188 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Origin and evolution of widespread crescentic pockmarks on the western South China Sea margin(2024-09-05); ; Pockmarks are prominent morphological features formed by fluid escape at the seafloor that provide valuable information on past environmental conditions and ongoing sedimentary processes, and they are also biodiversity hotspots and pose potential hazards in marine environments. Crescentic pockmarks are widespread on the present seafloor of the western South China Sea margin, however, their formation mechanisms are still poorly constrained. Here, we have imaged and investigated 116 crescentic pockmarks based on multibeam bathymetry and three-dimensional seismic data to gain insights into their origin and development processes. Crescentic pockmarks show asymmetrical geometries in cross-section and their opening directions are mainly oriented NW to NNW. Morphological analysis shows the presence of two types of composite styles, and the ratios between their widths and lengths are approximately ∼0.47. Seismic profiles crossing the crescentic pockmarks illustrate that their position has a trend of downslope migration. Time slices extracted from seismic data reveal that they exhibit as circular depressions in the deep strata, while they become crescentic gradually towards the shallow strata. We consider that the crescentic pockmarks may evolve from deep circular pockmarks and the intensity of fluid escape has played a vital role in affecting their morphologies. Downslope migration of these pockmarks might be influenced by the downslope bottom currents and turbidity currents, leading to more deposition in their upstream side and erosion in the downstream counterpart. Our study demonstrates how bottom currents and gravity flows rework pockmarks’ seafloor expression to form the crescentic morphologies. Hence, it provides a world-class morphological current indicator for other modern and paleo-pockmarks on continental margins worldwide.Wissenschaftlicher ArtikelBand:170113 26 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Channel inception through bottom‐current erosion of pockmarks revealed by numerical simulation(2023-04-23); ; ; ; In deep-marine environments, the inception of channels can be induced by the interaction between bottom currents and rough topography. However, it is still unclear under which conditions such features can form and what happens in the earliest phase of channel development. In this study, based on the morphological, sedimentary and oceanographic settings of a pockmark field in the NW South China Sea, we reveal the process of channel inception through the erosion of pockmarks by bottom currents. Using numerical simulations, we show that an appropriate current velocity can induce the erosion of pockmark trains in cohesive sediments, leading to the coalescence of discrete pockmarks and the formation of a channel with a rough thalweg. The interaction of bottom currents with the pockmarks induces a significant erosion along the pockmarks axis. Bottom current erosion is strongest at the downstream edges of pockmarks, where the horizontal velocity reaches a maximum and an upwelling forms. Erosion increases as the distance between pockmarks reduces. In our simulation results, a channel is only formed by the coalescence of pockmarks if the distance between pockmarks is <6 times the diameter of the pockmark. This study provides evidence of the formation of channels by bottom currents, which helps reconstruct paleoceanographic conditions based on sediment architecture. It also shows the complex hydrodynamics at these structures that strongly control sedimentary processes and may affect distribution of benthic ecosystems in marine environments.Wissenschaftlicher Artikel210 236 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Evolution of a buried moat–drift system in the Ewing Terrace uncovering highly dynamic bottom currents at the Argentine margin from the early Oligocene to middle Miocene(Society for Sedimentary Geology, 2024-11-23); ; ; ; The Ewing Terrace is a relatively flat surface formed by the action of bottom-currents and part of a Contourite Depositional System (CDS) at the Argentine continental slope. It is situated in a highly complex oceanographic setting at the Brazil-Malvinas Confluence Zone. Located in water depths of ~1000–1200 m and incised by the Mar del Plata Canyon, the Ewing Terrace is separated into the Northern Ewing Terrace (NET) and the Southern Ewing Terrace (SET). The long-term variations in ocean circulation led to a complex internal architecture of the terrace. As a result, this region represents a unique archive for studying sedimentary features that were eroded, transported, and deposited by along- and down-slope processes. An in-depth data analysis of high-resolution multichannel seismic profiles exhibits a complex sequence of erosional and depositional contouritic features, namely buried moat-drift systems identified in depths of ~ 370-750 m below the seafloor. They are arranged in migrating sequences and clustered in the Early Oligocene to Middle Miocene. This pattern is probably attributable to the vertical shift of water masses and to a highly dynamic oceanographic setting with spatial changes influenced by the Brazil-Malvinas Confluence Zone over this particular geological time. The moat-drift systems reveal significant lateral changes from north to south. In the southern area of the SET, the moats are constructional, and the associated separated mounded drifts are well developed. In contrast, the northern area exhibits two types of moats, reminiscent of cut-and-fill structures that mirror the significant and rapid changes in bottom current dynamics. With these new insights, this study contributes to a better understanding of moat-drift systems and improves the knowledge about past oceanographic dynamics and sediment deposition at the northern Argentine margin.Wissenschaftlicher ArtikelBand:94Heft:660 55