Geochronology and geochemistry of the northern Scotia Sea: A revised interpretation of the North and West Scotia ridge junction

The Cenozoic tectonic evolution of the Scotia Sea area

10.5194/egusphere-egu2020-178 ◽

2020 ◽

Author(s):

Anne Oldenhage ◽

Anouk Beniest ◽

Wouter P. Schellart

Keyword(s):

Tectonic Evolution ◽

Drake Passage ◽

Sea Level Changes ◽

Scotia Sea ◽

Scotia Ridge ◽

The North ◽

Reconstruction Software ◽

Circumpolar Current ◽

Global Sea Level ◽

The Antarctic

The breakup of the southern edge of Gondwanaland resulted in the formation of the Scotia Plate and the opening of Drake Passage throughout the Cenozoic. During the same period, the Tasman Seaway opened, although the timing of this opening is much better constrained. Rapid cooling of the Antarctic continent followed the openings of Drake Passage and the Tasman Seaway. The opening of Drake Passage or the Tasman seaway allowed the onset of the Antarctic Circumpolar Current, which is held responsible for the late Miocene global cooling, but discussions about the most important opening are still ongoing.The opening of Drake Passage and the development of the Scotia plate have been studied in multitude, but paleogeographic reconstructions show many differences and inconsistencies in both timing of opening Drake Passage as well as paleo-locations of crustal segments. The paleogeographic or tectonic reconstructions of the opening of Drake Passage and the formation of the Scotia plate are hard to compare, because differences in shapes of crustal segments, geographic projections and relative movements of segments chosen by previous authors make it difficult to observe similarities and differences between the different reconstructions.We present a thorough analysis of the previously published paleogeographic reconstructions with the aim to identify agreements and inconsistencies between these reconstructions. We re-defined the crustal segments that formed after the break-up of Gondwanaland by re-interpreting the bathymetry and magnetic anomalies of the study area. We re-modelled and compared georeferenced reconstructions from earlier studies in GPlates plate reconstruction software using our own defined crustal segments.This comparison shows that the different reconstructions agree quite well along the South Scotia Ridge, but that the North Scotia Ridge shows significant variations between different reconstructions or is not even considered in the reconstructions. Also, the nature and age of the crust of the Central Scotia Sea is heavily discussed, resulting in different opening scenarios. We argue that the tectonic evolution of the North Scotia Ridge and Central Scotia Sea is a crucial factor in identifying the timing of the development of an ocean gateway. We made a new tectonic reconstruction of the North Scotia Ridge crustal segments with less overlaps and gaps between the reconstructed crustal segments.The next step would be to compare the global sea-level changes and paleo-bathymetry with the different opening scenarios. Because we standardized all scenarios with the same crustal segments, we will then be able to provide opening ages of Drake Passage for the different scenarios that can be compared in a quantitative way.

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Geodynamic implications of the Cenozoic stress field on Seymour Island, West Antarctica

Antarctic Science ◽

10.1017/s0954102007000892 ◽

2008 ◽

Vol 20 (2) ◽

pp. 173-184 ◽

Cited By ~ 2

Author(s):

A. Maestro ◽

J. López-Martínez ◽

F. Bohoyo ◽

M. Montes ◽

F. Nozal ◽

...

Keyword(s):

Stress Field ◽

Antarctic Peninsula ◽

Horizontal Stress ◽

Weddell Sea ◽

Scotia Sea ◽

Compressional Stress ◽

The North ◽

Stress States ◽

Bransfield Basin ◽

Minimum Horizontal Stress

AbstractPalaeostress inferred from brittle mesostructures in Seymour (Marambio) Island indicates a Cenozoic to Recent origin for an extensional stress field, with only local compressional stress states. Minimum horizontal stress (σ3) orientations are scattered about two main NE–SW and NW–SE modes suggesting that two stress sources have been responsible for the dominant minimum horizontal stress directions in the north-western Weddell Sea. Extensional structures within a broad-scale compressional stress field can be linked to both the decrease in relative stress magnitudes from active margins to intraplate regions and the rifting processes that occurred in the northern Weddell Sea. Stress states with NW–SE trending σ3are compatible with back-arc extension along the eastern Antarctic Peninsula. We interpret this as due to the opening of the Larsen Basin during upper Cretaceous to Eocene and to the spreading, from Pliocene to present, of the Bransfield Basin (western Antarctic Peninsula), both due to former Phoenix Plate subduction under the Antarctic Plate. NE–SW σ3orientations could be expressions of continental fragmentation of the northern Antarctic Peninsula controlling eastwards drifting of the South Orkney microcontinent and other submerged continental blocks of the southern Scotia Sea.

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Geotectonic evolution of the Bransfield Basin, Antarctic Peninsula: insights from analogue models

Antarctic Science ◽

10.1017/s095410200800093x ◽

2008 ◽

Vol 20 (2) ◽

pp. 185-196 ◽

Cited By ~ 7

Author(s):

M.A. Solari ◽

F. Hervé ◽

J. Martinod ◽

J.P. Le Roux ◽

L.E. Ramírez ◽

...

Keyword(s):

Antarctic Peninsula ◽

South Shetland Islands ◽

The South ◽

The West ◽

Shetland Islands ◽

Scotia Ridge ◽

The North ◽

Analogue Models ◽

Bransfield Basin ◽

The Phoenix

AbstractThe Bransfield Strait, located between the South Shetland Islands and the north-western end of the Antarctic Peninsula, is a back-arc basin transitional between rifting and spreading. We compiled a geomorphological structural map of the Bransfield Basin combining published data and the interpretation of bathymetric images. Several analogue experiments reproducing the interaction between the Scotia, Antarctic, and Phoenix plates were carried out. The fault configuration observed in the geomorphological structural map was well reproduced by one of these analogue models. The results suggest the establishment of a transpressional regime to the west of the southern segment of the Shackleton Fracture Zone and a transtensional regime to the south-west of the South Scotia Ridge by at least c. 7 Ma. A probable mechanism for the opening of the Bransfield Basin requires two processes: 1) Significant transtensional effects in the Bransfield Basin caused by the configuration and drift vector of the Scotia Plate after the activity of the West Scotia Ridge ceased at c. 7 Ma. 2) Roll-back of the Phoenix Plate under the South Shetland Islands after cessation of spreading activity of the Phoenix Ridge at 3.3 ± 0.2 Ma, causing the north-westward migration of the South Shetland Trench.

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

10.5194/egusphere-egu2020-2083 ◽

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

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.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.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.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.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.

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

Global and Planetary Change ◽

10.1016/j.gloplacha.2021.103615 ◽

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

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The collision complex of the North Scotia Ridge

Journal of Geophysical Research Atmospheres ◽

10.1029/jb087ib05p03731 ◽

1982 ◽

Vol 87 (B5) ◽

pp. 3731 ◽

Cited By ~ 41

Author(s):

William J. Ludwig ◽

Philip D. Rabinowitz

Keyword(s):

Collision Complex ◽

Scotia Ridge ◽

The North

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Author Correction: Continuous moulting by Antarctic krill drives major pulses of carbon export in the north Scotia Sea, Southern Ocean

Nature Communications ◽

10.1038/s41467-021-22037-y ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

C. Manno ◽

S. Fielding ◽

G. Stowasser ◽

E. J. Murphy ◽

S. E. Thorpe ◽

...

Keyword(s):

Southern Ocean ◽

Antarctic Krill ◽

Carbon Export ◽

Scotia Sea ◽

The North

A Correction to this paper has been published: https://doi.org/10.1038/s41467-021-22037-y

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Continuous moulting by Antarctic krill drives major pulses of carbon export in the north Scotia Sea, Southern Ocean

Nature Communications ◽

10.1038/s41467-020-19956-7 ◽

2020 ◽

Vol 11 (1) ◽

Author(s):

C. Manno ◽

S. Fielding ◽

G. Stowasser ◽

E. J. Murphy ◽

S. E. Thorpe ◽

...

Keyword(s):

Southern Ocean ◽

Antarctic Krill ◽

Deep Ocean ◽

Carbon Export ◽

Scotia Sea ◽

Faecal Pellets ◽

The North ◽

Poc Flux ◽

Moulting Cycle

AbstractAntarctic krill play an important role in biogeochemical cycles and can potentially generate high-particulate organic carbon (POC) fluxes to the deep ocean. They also have an unusual trait of moulting continuously throughout their life-cycle. We determine the krill seasonal contribution to POC flux in terms of faecal pellets (FP), exuviae and carcasses from sediment trap samples collected in the Southern Ocean. We found that krill moulting generated an exuviae flux of similar order to that of FP, together accounting for 87% of an annual POC flux (22.8 g m−2 y−1). Using an inverse modelling approach, we determined the krill population size necessary to generate this flux peaked at 261 g m−2. This study shows the important role of krill exuviae as a vector for POC flux. Since krill moulting cycle depends on temperature, our results highlight the sensitivity of POC flux to rapid regional environmental change.

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