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1 All-Russia Research Institute for Geology and Mineral Resources of the World Ocean (VNIIOkeangeologia), 1 Angliysky Ave., 190 121 St Petersburg, Russia
2 Alfred-Wegener-Institut für Polar-und Meeresforschung (AWI), Columbusstrasse, D-2850 Bremerhaven, Germany
3 Polar Marine Geological Research Expedition (PMGRE), 24 Pobeda St., 189 510 Lomonosov, Russia
Interpretation of combined data sets, collected by Russian and German expeditions in the eastern Weddell Sea (EWS), was carried out to give new insight into the problem of early Gondwana breakup. Dominant features of the EWS margin are an initial rift structure which is flanked by a wedge of seaward dipping reflectors. The latter seems to be a volcanic sequence extruded near the continent-ocean boundary and underlain by a dyke suite, part of which is injected through the adjacent normal continental crust. Onset of rifting in the EWS was associated with the emplacement of a mantle plume which further weakened the lithosphere leading to its breakup and excessive production of igneous material. There is a regional correlation between the extent of the mantle thermal anomaly around the plume and tectonic processes (intensity of magmatism, crustal uplift, manner of rifting) which tend to attenuate away from the plume centre. Rearrangement of seafloor spreading, including a ridge jump, followed the initial rifting phase. Opening of EWS during Late Jurassic time resulted in the formation of an oceanic basin more than 400 km wide. By the end of Late Jurassic time this basin was obliquely cut off by a transcurrent fault due to plate reorganisation and movement of Antarctica southward. This regime ended in the Early Cretaceous when new spreading in the Weddell Sea overlapped the transform boundary.
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This 250-word extract was created in the absence of an abstract.
