Eocene to Miocene geometry of the West Antarctic Rift System

Seamounts off the West Antarctic margin: A case for non-hotspot driven intraplate volcanism

“…However, magnetic seafloor spreading data imply that this is a tectonic scar caused by a westward jump of the Pacific-Phoenix ridge at chron C27 (Larter et al, 2002;Eagles et al, 2004a). Müller et al (2007) suggested that this zone of possible lithospheric weakness was reactivated by a northward extension of a later WARS branch (Figs. 1 and 2h).…”

Deciphering tectonic phases of the Amundsen Sea Embayment shelf, West Antarctica, from a magnetic anomaly grid

“…In any case, the orientation of the identified sub-basin on the eastern ASE shelf (annotated as 'WARS rift basin' in Fig. 7) infers that it may be related to eastern WARS motion, possibly active as early as 55 Ma and lasting until at least 30 Ma before the zone of translateral deformation migrated or jumped eastward to join the triple junction at the spreading ridge colliding with the convergent margin of the southern Antarctic Peninsula as postulated by Müller et al (2007). Somewhat more speculative, but not unrealistic, is a correlation of the sub-basin with the dextral transtensional strain in western Marie Byrd Land observed by Siddoway (2008), who interprets this strain as an expression of an early WARS activity in the Late Cretaceous.…”

“…The basin, therefore, might be interpreted as having a half-graben geometry, with a bounding basement-involved normal fault zone on its southeastern edge, and a downthrown floor characterised by broad flexure northwestward away from the fault zone. The Palaeogene plate tectonic model of Müller et al (2007) predicts that a crustal boundary with this orientation would have responded to West Antarctica-East Antarctica relative motion along the WARS in right-lateral strike-slip motion. They suggest that this boundary extended from the Bentley Subglacial Trough and Byrd Subglacial Basin across western Ellsworth Land and the Thurston Island block, where it continues into the area of the dominant north-trending gravity anomaly lineaments of the Bellingshausen Sea.…”

“…Jordan et al (2010) invert airborne gravity data to reveal an extremely thin crust and low lithospheric rigidity beneath the onshore Pine Island Rift. Müller et al (2007) and Eagles et al (2009) considered how, at times between chrons 21 and 8 (48-26 Ma), the West Antarctic Rift System east of the Ross Sea operated in either dextral strike-slip or extensional motion through the region to the south and east of the Amundsen Sea Embayment connecting eventually to a Pacific-PhoenixEast Antarctic triple junction via the Byrd Subglacial Basin and the Bentley Subglacial Trench. There are indications for an early West Antarctic Rift System extension in western Marie Byrd Land in the mid-Cretaceous (e.g.…”

Rift processes and crustal structure of the Amundsen Sea Embayment, West Antarctica, from 3D potential field modelling

“…Müller et al (2007) considered that the WARS east of the Ross Sea started acting in dextral strike-slip or extensional motion east of the embayment between chrons 21 and 8 (48-26 Ma.). They postulated that this motion was connected to a PacificPhoenix-East Antarctica triple junction at the southwestern Bellingshausen Sea margin via the Bentley Subglacial Trench (Fretwell et al 2013) and the Byrd Subglacial Basin.…”