A marine geophysical reconnaissance of the Weddell Sea

Barker, Peter F.; Jahn, Rainer

doi:10.1111/j.1365-246x.1980.tb02620.x

Cited by 18 publications

(10 citation statements)

References 36 publications

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“…From the interpretation of marine geophysical data (seismic and gravity), Rogenhagen and Jokat [2000] confirm the interpretation of Anomaly T as being related to a decrease in spreading velocity during the opening between SAM and ANT. However, they are able to show that this gravity anomaly is not caused by a basement step as proposed by Livermore and Hunter [1996], or an inactive ridge as suggested by Barker and Jahn [1980].…”

Section: Introductionmentioning

confidence: 71%

“…The processing and interpretation of these lines are discussed by Jokat et al [2003a]. Farther west in the Weddell Sea ship track data were digitized from early expeditions carried out by the British Antarctic Survey (BAS) between 1974 and 1980 [ Barker and Jahn , 1980]. An extensive aeromagnetic data set from the southernmost parts of the Weddell Sea and onshore Dronning Maud Land was provided by the Polar Marine Geological Research Expedition (PMGRE, Russia) carried out in the years 1979 to 1989 [ Masolov , 1980; Golynsky and Aleshkova , 2000].…”

Section: Databasementioning

confidence: 99%

“…On the basis of these ambiguous data, a great number of different and differing models for the early opening of the Weddell Sea and the tectonic evolution of its neighboring continents have been developed in the last 25 years [ Barker and Jahn , 1980; LaBrecque and Barker , 1981; Martin et al , 1982; Martin and Hartnady , 1986; Lawver et al , 1992; Storey et al , 1996; Ghidella and LaBrecque , 1997; LaBrecque and Ghidella , 1997; Ghidella et al , 2002; Kovacs et al , 2002]. Some of these models describe the early breakup of Gondwana as a two‐plate problem between rigid East (ANT, India, Madagascar) and West Gondwana (AFR and SAM) plates [ Lawver et al , 1992; Livermore and Hunter , 1996; Reeves and de Wit , 2000].…”

Section: Introductionmentioning

confidence: 99%

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The Mesozoic breakup of the Weddell Sea

2006

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A new set of rotations is presented that describes a refined model for the early opening of the Weddell Sea between South America and Antarctica and the Mesozoic breakup of Gondwana. Published high‐resolution aeromagnetic data from the eastern Weddell Sea and additional track data farther west in the Weddell Sea were used to constrain the new model for the opening of the Weddell Sea. Rotation parameters derived for the South America–Antarctica spreading regime were combined with constraints on the South America–Africa and Africa‐Antarctica spreading systems to calculate a refined model for the Mesozoic breakup of Gondwana. Thereafter, at the time when the north‐south oriented separation between Africa and Antarctica is initiated by rifting in the Somali and Mozambique basins (∼167 Ma), stretching and extension takes place in a basin comprising continental crust of the Filchner‐Ronne Shelf, the Falkland Island block and the Maurice Ewing Bank. The first true ocean floor in the Weddell Sea is formed at about 147 Ma, after rifting between the Antarctic Peninsula and southernmost South America occurred. This is about 15–20 Myr later than previously estimated. Separation between South America and Antarctica takes place at slow spreading rates (14–12 mm/yr half rate) from 147 to 122 Ma and after 122 Ma (M2) at ultraslow spreading rates (∼8 mm/yr half rate) with little change in the NNW spreading direction throughout this time. A revised age range is proposed for the formation of the Explora Wedge (150–138 Ma), which is more than 30 Myr later than previously published (∼183 Ma).

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Section: Introductionmentioning

confidence: 71%

Section: Databasementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The Mesozoic breakup of the Weddell Sea

2006

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“…Norton & Sclater 1979;Lawver, Sclater & Meinke 1985), show South American-Antarctic motion to have been originally closer to north-south, and to have swung through NW-SE to the present W-E orientation through the Cretaceous and Cenozoic. The details of this change in orientation are poorly constrained, but fracture zone topography (Barker & Jahn 1980;Tectonic Map 1985) and magnetic anomalies (LaBrecque & Barker 1981) in the Weddell Sea provide independent corroboration. The level of description of South American-Antarctic motion provided by these models is adequate for many purposes, but not for all.…”

Section: Introductionmentioning

confidence: 99%

South American-Antarctic plate motion over the past 50 Myr, and the evolution of the South American-Antarctic ridge

Barker

Lawver

1988

Geophysical Journal International

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SUMMARY Magnetic and bathymetric data from the South American‐Antarctic plate boundary east of the South Sandwich trench have been interpreted to produce ocean floor ages, spreading rates and directions. SAM‐ANT motion over the past 50 Myr has been slow (10‐15 mm yr‐1 half rates). About 20 Ma the spreading direction changed from 120°‐300° to the present E‐W. These results have been combined with similar data from the South Atlantic and Southwest Indian Oceans to calculate six poles and rates of SAM‐ANT motion covering the past 50 Myr. The change at 20 Ma appears to have originated the long‐offset Bullard and South Sandwich fracture zones. The change may have been facilitated, or even triggered, by ridge crest‐trench collision along the South Scotia Ridge, east of the South Orkney Islands. This event however, could not alone have caused a stable change. It is concluded that the global balance of forces may for long periods be imperfectly reflected in plate motions, because of the constraining effects of long fracture zone offsets on the directions of plate motion, and that the ‘causes’ of abrupt changes in direction may precede them by several million years.

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“…Anomaly C34 (83Ma on the timescale of Cande & Kent 1995) was observed traversing the Weddell Sea from W to E, with a sequence of younger anomalies to the N. Older anomalies, however, were more difficult to identify, and various interpretations have been made (Barker & Jahn 1980;LaBrecque & Barker 1981;La Brecque et al 1989).…”

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confidence: 99%

Mesozoic seafloor spreading in the southern Weddell Sea

Livermore

Hunter

1996

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A re-evaluation of Weddell Sea magnetic anomaly data, in the light of satellite gravity maps, provides important constraints on plate kinematics prior to chron C34 (83Ma). Although M-series anomalies are difficult to identify, the evidence favours younger ages than previously suggested, based on the assumption that these anomalies formed at the South America-Antarctica plate boundary. Geosat-derived free-air gravity maps show a distinct anomaly, 'Anomaly-T', associated with the southern termination of a herring-bone pattern of flow lines. The associated magnetic anomaly has been identified previously as anomaly M20, on the basis of a model of very slow spreading, but is interpreted here as an edge-effect, associated with an abrupt decline in spreading rate which occurred between M4 (126 Ma) and M0 (118 Ma), and which induced the fine segmentation pattern to the north. Although anomalies are present to the south of Anomaly-T, they are of reduced amplitude, and are difficult to correlate over distances of more than c. 100km. Nevertheless, they appear to strike approximately W-E, sub-parallel to the younger anomalies to the north, and show a resemblance to anomalies M4-M12, modelled at a rate of 15 km Ma -1.Flow-line modelling, based on published rotations for the Southwest Indian Ridge and southern Mid-Atlantic Ridge, gives a reasonable fit to the observed trends of Weddell Sea gravity ridges. Two alternative models for the M-series reconstruction of Africa and Antarctica are employed, corresponding to the two M2 fits suggested by Bergh. Although it is not possible to reject either of the models, the tighter fit of the two gives slightly better agreement with Weddell Sea trends. In both models, a drop in rates occurs at M0 time.Anomalies farther south correspond with previously identified features, such as the Orion, Explora and Andenes anomalies, and the Polarstern Bank, all characterized by magnetic anomaly highs, attributed to excess volcanism during early break-up.

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A marine geophysical reconnaissance of the Weddell Sea

Cited by 18 publications

References 36 publications

The Mesozoic breakup of the Weddell Sea

The Mesozoic breakup of the Weddell Sea

South American-Antarctic plate motion over the past 50 Myr, and the evolution of the South American-Antarctic ridge

Mesozoic seafloor spreading in the southern Weddell Sea

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