Yu, Kaiqi
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Item type:Publication, 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.journal articleBand:48Heft:e2021GL092861179 190 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, 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.journal article253 57 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, 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.journal article209 235