Sudbury Basin Sediments and the Meteoritic Impact Theory of Origin for the Sudbury Structure

1975 ◽  
Vol 12 (4) ◽  
pp. 629-635 ◽  
Author(s):  
F. W. Beales ◽  
G. P. Lozej
Keyword(s):  
Marine Environment ◽  
Large Impact ◽  
Bottom Current ◽  
Meteoritic Impact ◽  
Basin Structure ◽  
Sea Bottom ◽  
Sudbury Structure ◽  
Impact Theory ◽  
Current Circulation

The Whitewater Group preserved within the Sudbury Basin structure conforms to a logical succession of beds to be expected for sediments accumulated in a large impact-generated crater. The lowest beds of the Group, the lower Onaping Formation, represent impact-generated breccia and fall-back material, the upper Onaping Formation and the overlying Onwatin Slates represent the restricted crater series, while the succeeding Chelmsford Sandstone represents an open marine turbidite sequence. The turbidites swept across the area at a time when the crater rim was no longer influencing sea bottom current circulation. The apparent anomaly of the occurrence of sediments deposited in an extensive marine environment and presently only found within the Sudbury Basin is attributed to preferential preservation, due to compaction-generated subsidence over the crater and impact-fractured area.

Anthropogeomorphology of marine fisheries in India: understanding the critical roles of Marine Fishery Advisories towards achieving SDG 14

2021 ◽  
Author(s):  
Sudip Kumar Kundu ◽  
Harini Santhanam
Keyword(s):  
Continental Shelf ◽  
Marine Environment ◽  
Search Time ◽  
Marine Fisheries ◽  
Anthropogenic Pressures ◽  
The Sustainable Development ◽  
Marine Fishery ◽  
Iuu Fishing ◽  
Sea Bottom ◽  
Marine Fishing

<p>The livelihoods of more than 30 per cent of the total population in India residing in nine maritime states and four Union Territories are dependent on the diverse ecosystem services offered by coastal and marine systems. Marine fisheries contribute significantly to the Indian economy through the foreign exchange from the export of seafood which corresponds to nearly 5 per cent of the overall export and 20 per cent of the agro-export. In recent times, the anthropogenic pressures due to extensive marine fishing introduce challenges in the marine environment. Marine anthropogeomorphology, capable of transforming the natural settings of the continental shelf dominantly, is often not studied in detail from the perspective of sustainable fishing. For example, the use of the assorted fishing gears can damage the sea floor, apart from the capture of juvenile and non-target fishes. Bottom trawling by mechanised crafts as a part of marine fishing affects the geomorphology of the continental shelf and continental slope by displacing boulders, interrupting the structure of the sediment column, resuspending sediments, and imprinting deep holes on the muddy sea bottom. Occasionally, the abandoned fishing nets/gears on the seafloor are also responsible for the geomorphological damages to the bottom of the sea and death of several marine benthic flora and fauna, a phenomenon referred to as ‘ghost fishing’. Further, Illegal, Unreported and Unregulated (IUU) fishing in the ocean also poses major threats for the marine environment. Thus, it is essential to quantify these impacts of anthropogeomorphology in order to achieve the targets of the Sustainable Development Goal (SDG) 14, promulgated by the United Nations Organisation. Marine Fishery Advisories, especially, Potential Fishing Zones (PFZ) advisories may be helpful in reducing the impacts by aiding sustainable harvesting of pelagic fishes under the current scenario. The ESSO-Indian National Centre for Ocean Information Services (INCOIS) is the nodal agency, which disseminates PFZ advisory since 1999 using remotely sensed datasets of sea surface temperature and chlorophyll-a to reduce the uncertainty during marine fishing. PFZ advisory can help to promote environment-friendly fishing by reducing the search time and hence, ensuring minimal damage to the marine environment.</p>

scholarly journals NEAR-BOTTOM CURRENT MEASURED BY ACOUSTIC SENSORS

1978 ◽  
Vol 1 (16) ◽  
pp. 50
Author(s):  
K.A. Selanger ◽  
T. Carstens
Keyword(s):  
Wave Theory ◽  
Current Data ◽  
Bottom Current ◽  
Acoustic Sensors ◽  
Current Profile ◽  
Vertical Transfer ◽  
First Order ◽  
Wave Measurements ◽  
Sea Bottom ◽  
Measuring Site

A vertical current profile has been measured with three acoustic meters 60 cm, 100 cm and 200 cm from the sea bottom. The depth at the measuring site was 84 metres. The profile is found to depend on the time scale of the water particle motion. An Ekman-like turning of the current is also observed, and the thickness of friction layers is estimated. Comparison of the current data with wave measurements indicates that the vertical transfer of surface wave energy is 30-50 per cent less than first order wave theory prescribes.

Sea bottom current activity recorded on the southern margin of the Vocontian basin (southeastern France) during the lower Aptian. Evidence for a climatic signal

2010 ◽  
Vol 181 (1) ◽  
pp. 3-18 ◽  
Author(s):  
Pierre Cotillon
Keyword(s):  
Spatial Distribution ◽  
Cold Water ◽  
Bottom Current ◽  
Temporary Increase ◽  
Large Area ◽  
Trade Winds ◽  
Southern Margin ◽  
Current Activity ◽  
Sea Bottom ◽  
Unconformity Surface

Abstract Numerous current marks are recorded on an Early Aptian unconformity surface observed over a large area of the Vocontian basin and its southern margin (southeastern France, Subalpine ranges). They occur in the transition zone between that basin and the adjacent Provence platform and correspond to various erosion marks, oriented biogenic remains (sponge spicules, belemnite rostra) and trace fossil directions (Rhizocorallium). Three local current orientations occur : 1) a westward orientation in the neritic zone, probably resulting from the trade winds that prevailed in the Tethyan domain; 2) a northward orientation in the deeper hemipelagic and pelagic zones probably resulting from a deviation of the westward currents by the Coriolis force; 3) a southward orientation in the eastern and western margins of the studied area, possibly induced by upwellings resulting from offshore northward deviated currents. These upwellings were characterized by cold water enriched with silica, phosphorous and organic matter. Some characteristics of the Early Aptian unconformity surface result from these different currents : 1) a specific type of erosion linked to mechanical and/or chemical features, 2) an erosion intensity displayed by the importance of the pre-Aptian stratigraphic gaps, 3) an erosion duration illustrated by the importance of the post-Aptian gaps. The spatial distribution of these features was controlled by the water-depth, depending locally on the occurrence of hemipelagic submarine reliefs of tectonic origin. Increases in current activity in the Early Aptian, linked to an acceleration of the atmospheric circulation, and highlighed by erosion and phosphatisation had previously been recorded for many other Eurasian and North Atlantic sites. This large spatial distribution suggests a global cause such as a temporary increase in the latitudinal thermal gradient and seasonal contrasts. According to the literature, these events may be related to the Early Aptian cooling, described by several authors in both high and low latitudes, which led to a remarkable pause in the middle Cretaceous warming.

Ferruginous bioforms accumulations in deep marine environments: an approach to their origin and formation mechanisms in the Transitional Zone province of the Galician Continental Margin (NW Iberian Peninsula)

2020 ◽  
Author(s):  
Ángel Enrique López-Pérez ◽  
Belén Rubio ◽  
Daniel Rey ◽  
Luís Pinheiro
Keyword(s):  
Steady State ◽  
Continental Margin ◽  
Deep Ocean ◽  
Direct Consequence ◽  
Transitional Zone ◽  
Ocean Floor ◽  
Bottom Current ◽  
Formation Mechanisms ◽  
Bottom Currents ◽  
Sea Bottom

<p>Ferruginous tubular structures concretions are widely distributed over the seafloor surrounding the <em>Gran Burato</em> depression in the Transitional Zone (TZ) province of the Galician Continental Margin (NW Iberian Margin). These bioforms-like structures are created by iron oxides precipitations into the tube-dwelling macrozoobenthos as a result of Fe<sup>2+</sup> upward diffusion and O<sub>2</sub> ventilation and diffusion acting in the water-sediment interphase in a non-steady state early diagenesis. X-ray diffraction analyses display that goethite is the main mineralogical component of these bioforms-like structures. Furthermore, non-steady state diagenesis has been identified by several oxidations fronts recognised in three piston cores, reflecting that the redoxcline has not achieved the deeper equilibrium in the study area. Afterwards, these ferruginous tubes were eroded, remobilised and redistributed over the seabed by bottom currents. Ocean-floor observations show erosion and sea-bottom current structures as ripples, grooves, erratic blocks, accumulations of pteropods and carbonate crusts associated with hardgrounds. Sedimentation rates calculated in a piston core display very low values for the last 30 cal ka BP (mean of 1.57 cm ky<sup>−1</sup>) with a marked hiatus between 17.80 to 10.45 cal ka BP, meanwhile abraded surfaces have been identified by high-resolution seismic data confirming erosional processes in this area of the TZ province. We conclude that the ferruginous bioforms accumulation over the deep-ocean floor is indicative of a present-day vigorous seafloor current acting and eroding the sediments of the TZ province. This bottom current is a direct consequence of the general seafloor elevation of the TZ province that causes constriction of the water masses (MOW and LSW) that induces a general intensification of the bottom currents and greater erosional capacity. This erosional process causes the continuous oxygenation of the upper sediments, and it prevents to reach the steady-state diagenesis, playing this fact an essential role in the ferruginous formations and accumulations in the study area.<br><br></p>

scholarly journals Development of a Towed Underwater Platform That Can Operate in a Marine Environment and Explore the Sea Bottom

2022 ◽  
Vol 10 (1) ◽  
pp. 66
Author(s):  
Sung-Jo Yun ◽  
Hyo-Gon Kim ◽  
Jung-Woo Park ◽  
Hyo-Jun Lee ◽  
Jong-Chan Kim ◽  
...  
Keyword(s):  
Marine Environment ◽  
Power Supply ◽  
High Speed ◽  
Underwater Vehicle ◽  
Environmental Constraints ◽  
Joint Operation ◽  
Unmanned Surface Vehicle ◽  
Unmanned Underwater Vehicle ◽  
Sea Bottom

Owing to environmental constraints, it is challenging to stably conduct various missions or surveys of the seabed for a prolonged period in the marine environment. To address this challenge, several devices and technologies are being developed. In this study, we aimed to develop an unmanned underwater vehicle (UUV)—specifically, a towed underwater platform—that can be loaded and unloaded via joint operation with an unmanned surface vehicle, which can be connected to a wired cable to obtain a stable power supply and high-speed communication. In addition, various sensors for detection are employed to investigate the marine environment and conduct missions. Furthermore, we operated the developed UUV in actual waters, reviewed the results, and examined its practical operability.

scholarly journals University of Kiel Radiocarbon Measurements VIII

Radiocarbon ◽  
1975 ◽  
Vol 17 (3) ◽  
pp. 276-300 ◽  
Author(s):  
H Erlenkeuser ◽  
H Metzner ◽  
H Willkomm
Keyword(s):  
Marine Environment ◽  
Research Program ◽  
Interdisciplinary Research ◽  
Short Term ◽  
Joint Research ◽  
Bottom Currents ◽  
Sea Bottom ◽  
Joint Research Program ◽  
Deutsche Forschungsgemeinschaft

The measurements presented in this list are part of the joint research program “Sonderforschungsbereich 95” of Kiel University for interdisciplinary research on problems of “Interaction Sea-Sea Bottom”, sponsored by the Deutsche Forschungsgemeinschaft. They are directed 1) to the study of the path of 14C from the atmosphere into argillaceous sediments, and 2) to date stratigraphic records within sediment. Associated problems are to identify sources of different 14C activity that contribute to recent deposits, and to learn about effects of morphologic and hydrographic factors, especially of bottom currents, on sedimentation sequence. Even short term processes can be successfully studied by analyses of bomb produced radiocarbon in the marine environment.

Structure Analysis on Artificial Reefs

2018 ◽  
Vol 874 ◽  
pp. 27-34
Author(s):  
Sapto P. Kertorahardjo ◽  
Harold Vincent ◽  
Putranta H. Duta
Keyword(s):  
Current Velocity ◽  
Concrete Structure ◽  
Dynamic Pressure ◽  
Permanent Deformation ◽  
Complex Structure ◽  
Artificial Reefs ◽  
Bottom Current ◽  
Stream Velocity ◽  
Practical Consideration ◽  
Sea Bottom

Most of the artificial reefs that have been developed in the world are the concrete structure. Regarding economical and practical consideration of artificial reefs, Indonesian government - Ministry of Marine Affairs and Fisheries - has proposed a new material to make an artificial habitats including artificial reefs made from polypropylene plastics (PP). However, diminishing approximately 80% of the weight structure compare to concrete structure has created new challenges to maintain the underwater structure with similar function. Moreover, the use of less weight material for artificial reefs structure will have impact on the structure responses.The structure responses due to sea bottom current and tidal stream velocity have been evaluated at several conditions. Dynamic pressure calculation was applied gradually as external load from a simple part to whole complex structure. Stresses and strains occur at some nodes as the structure critical area, within the same time frame, displacement of its elements describe physical characteristic response. Boundary conditions was encastred the sinker- bottom structure (U1 = U2 = U3 = UR1 = UR2 = UR3 = 0). In conclusion, for input of sea bottom current velocity u = 0.2 m/s the results for maximum stress are below the material’s yield stress hence its elasticity is relatively adequate to prevent permanent deformation. The result also showed some critical part of the structure that has high value on stress should be consider as the current velocity increase. Moreover increasing input and frontal area will significantly affect the drag force which will add load on the structure.

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