Shelfal sediment transport by an undercurrent forces turbidity-current activity during high sea level along the Chile continental margin

Geology ◽  
2016 ◽  
Vol 44 (4) ◽  
pp. 295-298 ◽  
Author(s):  
Anne Bernhardt ◽  
Dierk Hebbeln ◽  
Marcus Regenberg ◽  
Andreas Lückge ◽  
Manfred R. Strecker
Keyword(s):  
Sediment Transport ◽  
Sea Level ◽  
Continental Margin ◽  
Turbidity Current ◽  
Current Activity

Recurrence of turbidity currents on glaciated continental margins: A conceptual model from eastern Canada

2020 ◽  
Vol 90 (10) ◽  
pp. 1305-1321
Author(s):  
Alexandre Normandeau ◽  
D. Calvin Campbell
Keyword(s):  
Conceptual Model ◽  
Sea Level ◽  
Deep Water ◽  
Turbidity Current ◽  
Sediment Supply ◽  
Turbidity Currents ◽  
Continental Margins ◽  
Submarine Canyons ◽  
Eastern Canada ◽  
Current Activity

ABSTRACT Turbidity currents in submarine canyons transport large volumes of sediment and carbon to the deep sea and are known to present a major risk to submarine infrastructure. Understanding the origin, the triggers, the recurrence, and the timing of these events is important for predicting future events and mitigating their impact. Depending on the morphological and latitudinal setting of submarine canyons, different external controls will govern the recurrence of turbidity currents. Here, we assess the recurrence of turbidity currents in shelf-incising submarine canyons off eastern Canada in order to examine the effects of external forcings such as glacier retreat and sea level on the deep-water sedimentary record. We used multibeam bathymetry, sub-bottom profiles, and the analysis of turbidites in sediment cores to infer the triggers of turbidity currents over time and propose a conceptual model for the activity of turbidity currents during glacial retreat. The chronostratigraphy of turbidites shows that turbidity current activity in the glaciated The Gully submarine canyon (eastern Canada) was highest between 24 ka cal BP (LGM) and 17 ka cal BP, with > 100 turbidites per 1,000 yr, when the ice sheet was directly delivering sediment to submarine canyons. As the ice margin retreated, the dominant sediment supply switched to glaciofluvial and then to longshore drift, while RSL remained low. The recurrence of turbidity currents nonetheless decreased drastically to < 10 per 1000 yr during that time, pre-dating the rise in RSL. This timing suggests that the reduction of turbidity-current activity is closely linked to retreating glaciers rather than to sea-level rise, which occurred later. Following the retreat of the ice sheet, sea level rose progressively to drown the shallow banks on the continental shelf, and turbidity currents ceased being active after 13 ka cal BP. In the late Holocene, landslide and concomitant turbidity-current recurrence increased to 1 per 1,000 yrs, with at least four new events recorded in deep water. This study shows that glacial sediment supply and sea level controlled the type of sediment supply to the continental slope, which in turn controlled the triggers of turbidity currents over time and the flushing of sediment to the deep water. By comparing with other glaciated margins, we propose a conceptual model explaining the recurrence of turbidity currents, taking into account RSL change and the position of the ice margin relative to the shelf edge. This conceptual model can help predict turbidity-current activity and offshore geohazards on other ancient and modern glaciated continental margins.

Influence of Mantle Dynamic Topographical Variations on US Mid‐Atlantic Continental Margin Estimates of Sea‐Level Change

2021 ◽  
Vol 48 (4) ◽  
Author(s):  
William J. Schmelz ◽  
Kenneth G. Miller ◽  
Robert E. Kopp ◽  
Gregory S. Mountain ◽  
James V. Browning
Keyword(s):  
Sea Level ◽  
Continental Margin ◽  
Sea Level Change ◽  
Level Change

scholarly journals Coastal Flooding and Erosion under a Changing Climate: Implications at a Low-Lying Coast (Ebro Delta)

Water ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 346 ◽  
Author(s):  
Albert Grases ◽  
Vicente Gracia ◽  
Manuel García-León ◽  
Jue Lin-Ye ◽  
Joan Pau Sierra
Keyword(s):  
Climate Change ◽  
Sediment Transport ◽  
Sea Level ◽  
Anthropogenic Activities ◽  
Management Strategies ◽  
Wave Model ◽  
Ebro Delta ◽  
Coastal Hazards ◽  
Sand Transport ◽  
Storm Waves

Episodic coastal hazards associated to sea storms are responsible for sudden and intense changes in coastal morphology. Climate change and local anthropogenic activities such as river regulation and urban growth are raising risk levels in coastal hotspots, like low-lying areas of river deltas. This urges to revise present management strategies to guarantee their future sustainability, demanding a detailed diagnostic of the hazard evolution. In this paper, flooding and erosion under current and future conditions have been assessed at local scale at the urban area of Riumar, a touristic enclave placed at the Ebro Delta (Spain). Process-based models have been used to address the interaction between beach morphology and storm waves, as well as the influence of coastal environment complexity. Storm waves have been propagated with SWAN wave model and have provided the forcings for XBeach, a 2DH hydro-morphodynamic model. Results show that future trends in sea level rise and wave forcing produce non-linear variations of the flooded area and the volume of mobilized sediment resulting from marine storms. In particular, the balance between flooding and sediment transport will shift depending on the relative sea level. Wave induced flooding and long-shore sand transport seem to be diminished in the future, whereas static sea level flooding and cross-shore sediment transport are exacerbated. Therefore, the characterization of tipping points in the coastal response can help to develop robust and adaptive plans to manage climate change impact in sandy wave dominated coasts with a low-lying hinterland and a complex shoreline morphology.

Neotectonic evolution of the Brazilian northeastern continental margin based on sedimentary facies and ichnology,

2014 ◽  
Vol 82 (2) ◽  
pp. 462-472 ◽  
Author(s):  
Rosana Gandini ◽  
Dilce de Fátima Rossetti ◽  
Renata Guimarães Netto ◽  
Francisco Hilário Rego Bezerra ◽  
Ana Maria Góes
Keyword(s):  
Sea Level ◽  
Continental Margin ◽  
Sedimentary Facies ◽  
Passive Margin ◽  
South American ◽  
Soft Sediment ◽  
Rift Basins ◽  
Deformation Structures ◽  
Last Glaciation ◽  
Sediment Deformation

AbstractQuaternary post-Barreiras sediments are widespread along Brazil's passive margin. These deposits are well exposed in the onshore Paraíba Basin, which is one of the rift basins formed during the Pangean continental breakup. In this area, the post-Barreiras sediments consist of sandstones with abundant soft-sediment deformation structures related to seismicity contemporaneous with deposition. The trace fossilsThalassinoidesandPsilonichnusare found up to 38 m above modern sea level in sandstones dated between 60.0 (± 1.4) and 15.1 (± 1.8) ka. The integration of ichnological and sedimentary facies suggests nearshore paleoenvironments. Such deposits could not be related to eustatic sea-level rise, as this time coincides with the last glaciation. Hence, an uplift of 0.63 mm/yr, or 1.97 mm/yr if sea level was 80 m lower in the last glaciation, would have been required to ascend the post-Barreiras sediments several meters above the present-day sea level during the last 60 ka. This would suggest that the post-rift stage of the South American eastern passive margin may have experienced tectonic reactivation more intense than generally recognized. Although more complete data are still needed, the information presented herein may play an important role in studies aiming to decipher the Quaternary evolution of this passive margin.

Surface water productivity and sediment transport by Bering Strait throughflow in the Chukchi Shelf (the western Arctic Ocean) during the Holocene

The Holocene ◽  
2017 ◽  
Vol 28 (5) ◽  
pp. 814-826 ◽  
Author(s):  
Boo-Keun Khim ◽  
Mi Jung Lee ◽  
Hyen Goo Cho ◽  
Kwangkyu Park
Keyword(s):  
Surface Water ◽  
Sediment Transport ◽  
Sea Level ◽  
Water Productivity ◽  
Sediment Cores ◽  
Bering Strait ◽  
Biogenic Opal ◽  
The Holocene ◽  
Bering Strait Throughflow ◽  
Chukchi Shelf

Diverse paleoceanographic proxies from three sediment cores (GC12ex, JPC35, and JPC30) collected from the Chukchi Shelf north of the Bering Strait elucidate the Holocene paleoceanographic changes (surface water productivity and sediment transport) caused by the Bering Strait throughflow from the Bering Sea into the Chukchi Sea. Lithology of three sediment cores identified the same three units. Based on comparison and correlation to adjacent age-dated cores as well as AMS 14C dates of core GC12ex, the boundary between Unit 1 and Unit 2a is dated about 8500 cal. yr BP, and the boundary between Unit 2a and Unit 2b is also dated about 4500 cal. yr BP. Consistent down-core profiles of the geochemical and isotopic properties among the three cores differentiate the paleoceanographic conditions corresponding to lithologic units. Based on the biogenic opal, total organic carbon, and δ13C values, Unit 1 is characterized by low surface water marine productivity under relatively shallow water with weak transport of Bering Strait throughflow. Unit 2a shows a mixture of terrestrial and marine contributions, indicating the onset of increased marine surface water productivity after the main flooding (~11,500 cal. yr BP) of the Bering Strait by the Holocene sea-level rise. Unit 2b exhibits stable and enhanced marine biogenic opal production similar to the present-day oceanographic conditions. Such paleoceanographic changes were confirmed by the clay minerals (smectite, illite, kaolinite, and chlorite) and detrital isotopes (εNd and 87Sr/86Sr). Thus, the Bering Strait throughflow played an important role on surface water productivity and sediment deposition in the Chukchi Shelf in response to Holocene sea-level rise after the opening of the Bering Strait.

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