The Mesozoic breakup of the Weddell Sea

Abstract

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).

Deep-sea pre-glacial to glacial sedimentation in the Weddell Sea and southern Scotia Sea from a cross-basin seismic transect

“…2; Table 2; online Supplement 1) for the Weddell Sea and Scotia Sea from published literature (BAS, 1985;LaBrecque and Ghidella, 1997;Nankivell, 1997;Surinãch et al, 1997;Lodolo et al, 1998Lodolo et al, , 2010Bohoyo et al, 2002Bohoyo et al, , 2007Eagles and Livermore, 2002;Ghidella et al, 2002;Kovacs et al, 2002;Eagles et al, 2005Eagles et al, , 2006Galindo-Zaldívar et al, 2006;König and Jokat, 2006;Maldonado et al, 2007;Eagles, 2010). This map compilation has not been published before and is available in the PANGAEA database (Lindeque et al, 2012).…”

“…Sedimentation initially started in the Weddell Sea from~138 Ma onwards (Miller et al, 1990;Rogenhagen et al, 2004), as Africa and Antarctica separated (e.g. König and Jokat, 2006; Table 1). During the Early Eocene, Antarctica had a warm climate with high pCO 2 concentrations (>1800 ppm) and sea level was about 150 m higher than today (e.g.…”

“…The Eocene-Oligocene transition at~33 Ma signifies a period of several major changes: Antarctica's climate changed from warm and relatively ice-sheet free to cold and ice-covered, as temperatures decreased by about 4°C; pCO 2 declined rapidly from 1750 to 700 ppm and orbital cycles changed (Barker, 2001;Zachos et al, 2001;DeConto and Pollard, 2003;Barker and Thomas, 2004;Coxall et al, 2005;Livermore et al, 2005;Pollard and DeConto, 2009); the Antarctic Circumpolar Current (ACC) developed Gahagan, 1998, 2003;Miller et al, 2008) as the Weddell Sea and Drake Passage opened and western Scotia Sea started to open Ghidella et al, 2002;König and Jokat, 2006;Maldonado et al, 2006); ephemeral ice sheets formed the initial East Antarctic Ice Sheet (EAIS) and West Antarctic Ice Sheet (WAIS) on higher elevations Barker et al, 1988;Miller et al, 1990;Oszko, 1997;Barker, 2001) as well as small ice-caps on the northern Antarctic Peninsula Smith and Anderson, 2010;.…”

“…seismic stratigraphic units Pw5, Sh5, Maldonado et al, 2006) during the completion of the Weddell Sea opening (e.g. Bohoyo et al, 2002;König and Jokat, 2006; Table 1; Fig. 1).…”

“…König and Jokat, 2006). In regions where actual magnetic data picks were unavailable, published anomaly and isochron maps (e.g.…”