Opening history of Powell Basin, Antarctic Peninsula

Abstract

The opening of Powell Basin was part of the regional response to N55 ‡W relative plate motion of South America away from Antarctica, which led to the formation of Drake Passage during the Eocene and Oligocene. Restoration of microplates around the basin using gridded magnetic anomalies from its margins illustrates the pre-break-up continuity of the Pacific Margin Anomaly magnetic high associated with a Mesozoic arc-batholith. Newly compiled magnetic anomaly data over the Powell Basin show subdued linear seafloor spreading type anomalies. These are used, together with marginal and regional geology, to constrain the opening history of the basin. Magnetic reversal modelling suggests that slow spreading in Powell Basin probably occurred between 29.7 Ma and 21.8 Ma, following rifting of Mesozoic continental crust with associated break-up volcanism. A simple, two-phase model for the rotation of the South Orkney Microcontinent away from the Antarctic Peninsula accounts for the pattern of magnetic reversals recorded in Powell Basin, and for the structure of its margins. Crown

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).…”

“…Conflicting opinions do exist between studies in the same basin e.g. in the Powell Basin between Eagles and Livermore (2002) and Surinãch et al (1997) due to ambiguous data and allow for alternative age interpretations. In such cases, the most recent publication or best fit with the regional trend was favoured.…”

“…Ages appended with old (o), middle (m) and young (y); Chron-L and Age-L (literature) from: C5n to C33r, Cande and Kent, 1995;C34 to E, Barker, 2001C34 to E, Barker, , 1994M0 to M17, Kent and Gradstein 1986;Gradstein et al, 1994. References: 1 Maldonado et al, 2007;2 Bohoyo et al, 2002;3 Eagles and Livermore, 2002;4 Lodolo et al, 1998;5 Kovacs et al, 2002;6 Ghidella et al, 2002;7 Nankivell, 1997;8 LaBrecque and 9 König and Jokat, 2006. All ages are in Ma.…”

Animated tectonic reconstruction of the Southern Pacific and alkaline volcanism at its convergent margins since Eocene times

“…The animation shows the active parts of the spreading centre as a black line in the northern Weddell Sea. The cessation of subduction east of the Powell Basin resulted in the basin's extinction by around 20 Ma (Eagles and Livermore, 2002).…”

“…In addition to these, for this new animation we have included gridded data showing the onshore topography of South America (Smith and Sandwell, 1996), and gravity data showing the formation of the Powell Basin and motion of the Nazca plate east of the Chile Ridge. To do this we used rotation parameters for Antarctica-Nazca and Powell Basin relative motions taken from and Eagles and Livermore (2002). Small motions of the Hudson microplate (Eakins, 2002), and the Selkirk, Friday, and other microplates at the margins of the Nazca plate are not depicted as there are no rotations published to describe them, although the incorporated microplates are shown after their extinctions.…”