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

Manned Submersible ◽

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.

Grain growth behaviour and mechanical properties of coarse-grained cemented carbides with bimodal grain size distributions

Materials Science and Engineering A ◽

10.1016/j.msea.2020.140586 ◽

2020 ◽

pp. 140586

Author(s):

Rengui He ◽

Qiumin Yang ◽

Bin Li ◽

Jia Lou ◽

Hailin Yang ◽

...

Keyword(s):

Mechanical Properties ◽

Grain Size ◽

Grain Growth ◽

Coarse Grained ◽

Cemented Carbides ◽

Size Distributions ◽

Growth Behaviour ◽

The volcanological significance of deep-sea ash layers associated with ignimbrites

Geological Magazine ◽

10.1017/s0016756800028533 ◽

1980 ◽

Vol 117 (5) ◽

pp. 425-436 ◽

Cited By ~ 66

Author(s):

R. S. J. Sparks ◽

T. C. Huang

Keyword(s):

Deep Sea ◽

Eastern Mediterranean ◽

Eruption Column ◽

Size Distributions ◽

Ash Fall ◽

Column Collapse ◽

Median Diameter ◽

Bimodal Grain Size ◽

Fall Deposits

SummaryMany volcanic ash layers preserved in deep-sea sediments are the products of large magnitude ignimbrite eruptions. The characteristics of such co-ignimbrite ash-fall deposits are illustrated by two layers from the Eastern Mediterranean: the Minoan ash, Santorini, and the Campanian ash, Italy. These layers are divisible into a coarse lower unit and a fine upper unit in proximal cores. Both layers also show striking bimodal grain size distributions in more distal cores. The coarser mode decreases in median diameter with distance from source whereas the finer mode shows no lateral variation. These features are interpreted in terms of a model for ignimbrite formation by eruption column collapse. Comparable volumes of ignimbrite and associated air-fall ejecta are produced.

Three-Dimensional in situ Reconstructions of Microstructures with Bimodal Grain Size Distributions

Microscopy and Microanalysis ◽

10.1017/s1431927619002587 ◽

2019 ◽

Vol 25 (S2) ◽

pp. 370-371

Author(s):

Ashley Bucsek ◽

Lee Casalena ◽

Darren C. Pagan ◽

Partha P. Paul ◽

Yuriy Chumlyakov ◽

...

Keyword(s):

Grain Size ◽

Three Dimensional ◽

Size Distributions ◽

Mechanical characterization by traction and small punch tests of ultra-fine grained AISI 316L with bimodal grain size distributions

10.1063/1.5112699 ◽

2019 ◽

Author(s):

C. Keller ◽

B. Flipon ◽

M. Diez ◽

M. Serrano

Keyword(s):

Grain Size ◽

Mechanical Characterization ◽

Size Distributions ◽

Aisi 316L ◽

Small Punch ◽

Fine Grained ◽

Bimodal grain size distributions in UFG materials produced by SPD: Their evolution and effect on mechanical properties

Journal of Physics Conference Series ◽

10.1088/1742-6596/240/1/012147 ◽

2010 ◽

Vol 240 ◽

pp. 012147 ◽

Cited By ~ 19

Author(s):

H W Höppel ◽

M Korn ◽

R Lapovok ◽

H Mughrabi

Keyword(s):

Mechanical Properties ◽

Grain Size ◽

Size Distributions ◽

Modes of turbidite deposition deduced from grain-size analyses

Geological Magazine ◽

10.1017/s0016756800042771 ◽

1972 ◽

Vol 109 (6) ◽

pp. 491-500 ◽

Cited By ~ 13

Author(s):

A. T. Buller ◽

J. McManus

Keyword(s):

Grain Size ◽

Submarine Canyon ◽

Size Distributions ◽

Steep Gradient ◽

Water Layers ◽

The Matrix ◽

Grain Size Distributions

SummaryValues of quartile deviations (QDa) and medians (Mdmm) have been calculated from over 400 grain-size distributions of modern and ancient turbidites. Each QDa–Md pair is plotted on double-log paper to establish any distinctive trends. The QDa–Md analysis of modern turbidites reveals a steep gradient trend derived from the grain-size distributions of submarine canyon and delta fan sediments, and a shallow gradient trend derived from the grain-size distributions of samples from oceanic bottoms and nepheloid water layers. The QDa–Md analysis of ancient turbidites reveals two trends, but these do not coincide with their modern counterparts. The steeper gradient trend is related to distal and proximal turbidites, while the shallow trend is related to fluxoturbidites. The disparity between the ancient and modern QDa–Md analyses is caused by textural modifications of turbidites by diagenetic disintegration of unstable minerals. The alteration products are incorporated subsequently in the matrix. The diagenetic effects on the positions of the QDa–Md plots are demonstrated theoretically by computing the textural alteration of six modern turbidites by assuming that they will lose 20%, and then 40%, of their sand-sized particles to the matrix. By working in reverse the QDa–Md plots of ancient turbidites can be ‘restored’ to their diagenetically unaltered positions. Their restored positions correspond to the QDa–Md trends of modern turbidites.

Sintering shrinkage of WC–Co materials with bimodal grain size distributions

Acta Materialia ◽

10.1016/j.actamat.2004.12.016 ◽

2005 ◽

Vol 53 (6) ◽

pp. 1665-1671 ◽

Cited By ~ 29

Author(s):

A. Petersson ◽

J. Ågren

Keyword(s):

Grain Size ◽

Size Distributions ◽

Sintering Shrinkage ◽

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

10.31223/x57043 ◽

2021 ◽

Author(s):

Nan Wu ◽

Harya Nugraha ◽

Michael Steventon ◽

Fa Zhong

Keyword(s):

Late Miocene ◽

Submarine Canyon ◽

Turbidity Currents ◽

Submarine Canyons ◽

Seismic Reflection Data ◽

Reflection Data ◽

Depositional Processes ◽

Seabed Topography ◽

Gravity Driven ◽

Unconformity Surface

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.