Crustal structure beneath Discovery Bank in the Scotia Sea from group velocity tomography and seismic reflection data

2005 ◽  
Vol 17 (1) ◽  
pp. 97-106 ◽  
Author(s):  
A. VUAN ◽  
E. LODOLO ◽  
G.F. PANZA ◽  
C. SAULI
Keyword(s):  
Surface Wave ◽  
Group Velocity ◽  
Seismic Reflection ◽  
The South ◽  
Data Set ◽  
Scotia Sea ◽  
Scotia Ridge ◽  
Velocity Anomalies ◽  
Central Eastern ◽  
South Scotia Ridge

The Bruce, Discovery, Herdman and Jane banks, all located along the central-eastern part of the South Scotia Ridge, represent isolated topographic highs, surrounded by young oceanic crust (∼5–23 Ma), whose petrological and structural nature is still the subject of speculation due to the lack of relevant data. Surface wave tomography in and around the Scotia Sea region, performed using eight broadband seismic stations and 300 events, shows that the central-eastern part of the South Scotia Ridge is characterized by negative surface wave group velocity anomalies as large as 6% in the period range from 15 s to 50 s. The spatial resolution of our data set (∼300 km) makes it possible to study a specific area (centred at 61°S and 36°W) that includes Discovery Bank and appears to show dispersion characteristics similar to those found beneath the northern tip of the Antarctic Peninsula and southern South America. Surface wave dispersion curves are inverted to obtain 1-D isotropic shear wave velocity profiles that suggest a continental nature of Discovery Bank. Crustal thickness is in the range 23–28 km with a sub-Moho velocity of 4.1–4.2 km s−1. The boundaries of the negative group velocity anomalies are marked by a high level of seismic activity. The depth of the events and their large seismic moment suggest the presence of continental lithosphere. The continental-type crust of this topographic relief is supported by our interpretation of multichannel seismic reflection profiles acquired across this rise, where the observed seismic structures are interpreted as thinned and faulted continental plateau.

Geological mapping in the offshore domain: unravelling the tectonic history of the Scotia Sea

2020 ◽  
Author(s):  
Anouk Beniest ◽  
Wouter P. Schellart
Keyword(s):  
Cross Sections ◽  
Mantle Flow ◽  
The South ◽  
The West ◽  
Scotia Sea ◽  
Scotia Ridge ◽  
History Of ◽  
Geological Map ◽  
Velocity Anomalies ◽  
Sea Area

<p>We produced the first geological map of the Scotia Sea area based on the available geophysical and geological data. Combining magnetic, Bouguer gravity anomaly and high-resolution bathymetric data with geological data from dredged samples allowed us to map lithologies and structural features in this mostly submerged and complex tectonic area. This geological map allowed us to integrate a very inter-disciplinary dataset, thereby reviewing the available data and addressing some of the still persisting geological challenges and controversies in the area.</p><p>One of the most important and persistent discussions is the nature and age of the Central Scotia Sea. We mapped this part of the Scotia Sea as basaltic-andesitic lithology partly covered by thick, oceanic sediments. This differs in lithology from the West and East Scotia Sea, which we mapped as a basaltic lithology. Based on our lithological map, its unusual thickness and the presence of the Ancestral South Sandwich Arc (ASSA, early Oligocene-late Miocene) we argue that Central Scotia Sea has an Eocene to earliest Oligocene age.</p><p>Cross-sections combining the geology, crustal structure and mantle tomography reveal high velocity anomalies and colder mantle material below the structural highs along the South Scotia Ridge (Terror Rise, Pirie Bank, Bruce Bank and Discovery Bank) and below the South Sandwich Islands. We interpreted those as the southern, stagnated part of the subducting slab of the South Sandwich Trench, following the geometry of Jane Basin and the currently active subducting slab at the South Sandwich Trench. Low velocity anomalies are observed below Drake Passage and the East Scotia Sea, which are interpreted as warmer toroidal mantle flow around the slab edges below the Chilean trench and the South Sandwich trench.</p><p>Based on our geological map and integrated cross-sections we propose a multi-phase evolution of the Scotia Sea area with Eocene or older oceanic crust for the Central Scotia Sea. A first wide-rift-phase initiated before 30 Ma in the West Scotia Ridge, Protector Basin, Dove Basin and Jane Basin either as a result of the diverging South American and Antarctic continents and/or due to subduction rollback that commenced soon after subduction initiation that eventually caused the ASSA to form. The first full spreading center developed in the West Scotia Sea, aided by the warmer toroidal mantle flow causing spreading to be abandoned in the other basins (~30 Ma). A second rift phase in the fore-arc, in between the ASSA and the South Sandwich trench (~20 Ma), initiated through a redistribution of far-field forces as a result of continuous trench retreat. The warmer toroidal mantle concentrated on the East Scotia Ridge resulting in the second spreading system (15 Ma), abandoning the West Scotia Ridge spreading system 6-10 Ma.</p><p>We show that it is possible to create a geological map in a very remote area with an extreme environment with the available geological and geophysical data. This new way of producing geological maps in the offshore domain provides a better insight into the geological history of geologically complex areas that are largely submerged.</p>

Geochronology and geochemistry of the South Scotia Ridge: Miocene island arc volcanism of the Scotia Sea

2021 ◽  
pp. 103615
Author(s):  
Teal R. Riley ◽  
Alex Burton-Johnson ◽  
Philip T. Leat ◽  
Kelly A. Hogan ◽  
Alison M. Halton
Keyword(s):  
Island Arc ◽  
The South ◽  
Scotia Sea ◽  
Arc Volcanism ◽  
Scotia Ridge ◽  
Island Arc Volcanism ◽  
South Scotia Ridge

scholarly journals Metagenomic Characterization of the Viral Community of the South Scotia Ridge

2018 ◽  
Author(s):  
Qingwei Yang ◽  
Chen Gao ◽  
Jiang Yong ◽  
Ming Wang ◽  
Xinhao Zhou ◽  
...  
Keyword(s):  
Phylogenetic Analyses ◽  
Great Influence ◽  
Austral Summer ◽  
Taxonomic Composition ◽  
Marker Genes ◽  
The South ◽  
Scotia Ridge ◽  
Viral Communities ◽  
The Antarctic ◽  
South Scotia Ridge

Viruses are the most abundant biological entities in aquatic ecosystems and harbor an enormous genetic diversity. While their great influence on the marine ecosystems is widely acknowledged, current information about their diversity remains scarce. A viral metagenomic analysis of three water samples was conducted from sites on the South Scotia Ridge (SSR) near the Antarctic Peninsula, during the austral summer 2016. The taxonomic composition and diversity of the viral communities were investigated and a functional assessment of the sequences was determined. Phylotypic analysis showed that most viruses belonging to the order Caudovirales, especially the family Podoviridae (41.92-48.7%), similar to the viromes from the Pacific Ocean. Functional analysis revealed a relatively high frequency of phage-associated and metabolism genes. Phylogenetic analyses of phage TerL and Capsid_NCLDV (nucleocytoplasmic large DNA viruses) marker genes indicated that many sequences associated with Caudovirales and NCLDV were novel and distinct from known phage genomes. High Phaeocystis globosa virus virophage (Pgvv) signatures were found in SSR area and complete and partial Pgvv-like were obtained which may have an influence on host-virus interactions. Our study expands the existing knowledge of viral communities and their diversities from the Antarctic region and provides basic data for further exploring polar microbiomes.

Transtensional tectonics along the south Scotia Ridge, Antarctica

1996 ◽  
Vol 267 (1-4) ◽  
pp. 31-56 ◽  
Author(s):  
J. Acosta ◽  
E. Uchupi
Keyword(s):  
The South ◽  
Scotia Ridge ◽  
South Scotia Ridge

Water mass pathways and transports over the South Scotia Ridge west of 50°W

2012 ◽  
Vol 59 ◽  
pp. 8-24 ◽  
Author(s):  
Margarita Palmer ◽  
Damià Gomis ◽  
Maria del Mar Flexas ◽  
Gabriel Jordà ◽  
Loic Jullion ◽  
...  
Keyword(s):  
Water Mass ◽  
The South ◽  
Scotia Ridge ◽  
South Scotia Ridge

3D model of a sector of the South Scotia Ridge (Antarctica)

2009 ◽  
Vol 35 (1) ◽  
pp. 83-91 ◽  
Author(s):  
Sara Susini ◽  
Mauro De Donatis
Keyword(s):  
3D Model ◽  
The South ◽  
Scotia Ridge ◽  
South Scotia Ridge

scholarly journals 3D crustal structure of the Ligurian Basin revealed by surface wave tomography using ocean bottom seismometer data

Solid Earth ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 2597-2613
Author(s):  
Felix N. Wolf ◽  
Dietrich Lange ◽  
Anke Dannowski ◽  
Martin Thorwart ◽  
Wayne Crawford ◽  
...  
Keyword(s):  
Surface Wave ◽  
Group Velocity ◽  
Shear Wave ◽  
Shear Wave Velocity ◽  
Ambient Noise ◽  
Cross Correlation ◽  
Ocean Bottom ◽  
The South ◽  
Teleseismic Events ◽  
Ligurian Basin

Abstract. The Liguro-Provençal basin was formed as a back-arc basin of the retreating Calabrian–Apennines subduction zone during the Oligocene and Miocene. The resulting rotation of the Corsica–Sardinia block is associated with rifting, shaping the Ligurian Basin. It is still debated whether oceanic or atypical oceanic crust was formed or if the crust is continental and experienced extreme thinning during the opening of the basin. We perform ambient noise tomography, also taking into account teleseismic events, using an amphibious network of seismic stations, including 22 broadband ocean bottom seismometers (OBSs), to investigate the lithospheric structure of the Ligurian Basin. The instruments were installed in the Ligurian Basin for 8 months between June 2017 and February 2018 as part of the AlpArray seismic network. Because of additional noise sources in the ocean, OBS data are rarely used for ambient noise studies. However, we carefully pre-process the data, including corrections for instrument tilt and seafloor compliance and excluding higher modes of the ambient-noise Rayleigh waves. We calculate daily cross-correlation functions for the AlpArray OBS array and surrounding land stations. We also correlate short time windows that include teleseismic earthquakes, allowing us to derive surface wave group velocities for longer periods than using ambient noise only. We obtain group velocity maps by inverting Green's functions derived from the cross-correlation of ambient noise and teleseismic events, respectively. We then used the resulting 3D group velocity information to calculate 1D depth inversions for S-wave velocities. The group velocity and shear-wave velocity results compare well to existing large-scale studies that partly include the study area. In onshore France, we observe a high-velocity area beneath the Argentera Massif, roughly 10 km below sea level. We interpret this as the root of the Argentera Massif. Our results add spatial resolution to known seismic velocities in the Ligurian Basin, thereby augmenting existing seismic profiles. In agreement with existing seismic studies, our shear-wave velocity maps indicate a deepening of the Moho from 12 km at the south-western basin centre to 20–25 km at the Ligurian coast in the north-east and over 30 km at the Provençal coast. The maps also indicate that the south-western and north-eastern Ligurian Basin are structurally separate. The lack of high crustal vP/vS ratios beneath the south-western part of the Ligurian Basin preclude mantle serpentinisation there.

scholarly journals Surface Circulation at the Tip of the Antarctic Peninsula from Drifters

2009 ◽  
Vol 39 (1) ◽  
pp. 3-26 ◽  
Author(s):  
Andrew F. Thompson ◽  
Karen J. Heywood ◽  
Sally E. Thorpe ◽  
Angelika H. H. Renner ◽  
Armando Trasviña
Keyword(s):  
Antarctic Peninsula ◽  
Weddell Sea ◽  
Ecosystem Dynamics ◽  
Mean Flow ◽  
The South ◽  
Scotia Ridge ◽  
Surface Circulation ◽  
Dominant Feature ◽  
The Antarctic ◽  
South Scotia Ridge

Abstract An array of 40 surface drifters, drogued at 15-m depth, was deployed in February 2007 to the east of the tip of the Antarctic Peninsula as part of the Antarctic Drifter Experiment: Links to Isobaths and Ecosystems (ADELIE) project. Data obtained from these drifters and from a select number of local historical drifters provide the most detailed observations to date of the surface circulation in the northwestern Weddell Sea. The Antarctic Slope Front (ASF), characterized by a ∼20 cm s−1 current following the 1000-m isobath, is the dominant feature east of the peninsula. The slope front bifurcates when it encounters the South Scotia Ridge with the drifters following one of three paths. Drifters (i) are carried westward into Bransfield Strait; (ii) follow the 1000-m isobath to the east along the southern edge of the South Scotia Ridge; or (iii) become entrained in a large-standing eddy over the South Scotia Ridge. Drifters are strongly steered by contours of f /h (Coriolis frequency/depth) as shown by calculations of the first two moments of displacement in both geographic coordinates and coordinates locally aligned with contours of f /h. An eddy-mean decomposition of the drifter velocities indicates that shear in the mean flow makes the dominant contribution to dispersion in the along-f /h direction, but eddy processes are more important in dispersing particles across contours of f /h. The results of the ADELIE study suggest that the circulation near the tip of the Antarctic Peninsula may influence ecosystem dynamics in the Southern Ocean through Antarctic krill transport and the export of nutrients.

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