Reassembling Gondwana: A new high quality constraint from vibroseis exploration of the sub‐ice shelf geology of the East Antarctic continental margin

Abstract

The breakup of Gondwana is manifested by coeval early Jurassic Karoo magmatism in South Africa and East Antarctica. In South Africa, the large volumes of volcanic rocks of the adjoining Lebombo and Mwenetzi-Save monoclines represent a volcanic rift margin, and in East Antarctica, a corresponding feature, the Explora Wedge is buried below sediments and floating ice shelves on the continental margin of Dronning Maud Land. We use the seismic vibrator source to explore the sub-ice geology in Antarctica, and the new seismic reflection and available regional aeromagnetic data enable us to outline a dogleg landward extent of the Explora Wedge in Dronning Maud Land. The congruent inboard wedge geometries on the two continents define a high quality constraint, which facilitate for the first time, a geologically consistent and tight reconstruction of Africa relative to East Antarctica within Gondwana. The uncertainties in correlations of major geological features (mobile belts) from one continent to the other may now be of the order of ten's of kilometers rather than hundreds of kilometers.

New geophysical compilations link crustal block motion to Jurassic extension and strike-slip faulting in the Weddell Sea Rift System of West Antarctica

“…4b), and therefore prefer a simpler extensional or transtensional model for this region. An extensional model would be consistent with tectonic models for the earliest stages of rifting between South African and East Antarctica (Klausen, 2009;Kristoffersen et al, 2014). …”

“…The northern edge of the WSRS is marked by the Orion, Andenes and Explora magnetic anomalies (Fig. 1) which are interpreted to reflect a combination of Jurassic intrusions, underplate and thick seaward dipping lava sequences within the transition between continental and oceanic crust (Ferris et al, 2000;Golynsky and Aleshkova, 1997b;Kristoffersen et al, 2014). Berkner Island is also associated with a significant positive magnetic anomaly that may reflect a link between the Explora wedge and the Dufek mafic intrusion ( Fig.…”

“…Eastwards along strike from the NWMP is the Explora anomaly, linked to a narrow but highly magmatic rift zone, which developed during the initial separation between South Africa and East Antarctica, with coincident emplacement of Karoo magmas (Kristoffersen et al, 2014).…”

“…One key crustal block is the West Antarctic Ellsworth-Whitmore mountains crustal block (Elliot and Fleming, 2004); Dufek Intrusion (DI) (black/red check) (Ferris et al, 1998); Jurassic granites (red diamonds) (Storey et al, 1988b); Seismically imaged seaward dipping reflector sequences (SDR) (red hatch) (Kristoffersen et al, 2014); Orion, Andenes and Explora magnetic anomalies (OA, AA and EA) linked to Jurassic magmatism (Ferris et al, 2000;Golynsky and Aleshkova, 1997a)…”

Lithospheric Thickness of Volcanic Rifting Margins: Constraints From Seaward Dipping Reflectors

“…Following him, many authors have reported observations of SDRs including along North Atlantic margins (e.g., Mutter et al, ; Planke & Eldholm, ), South Atlantic margins (e.g., Elliott et al, ; Franke et al, ; Gladczenko et al, ), Indian margins (e.g., Calvès et al, ), Australian margins (e.g. Direen & Crawford, ), and Antarctica margins (e.g., Kalberg & Gohl, ; Kristoffersen et al, ). Tilted lava packages on Iceland (Bodvarsson & Walker, ) and parts of the Deccan traps (Watts & Cox, ) are on‐land SDRs analogues.…”