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Abstract

The Amundsen Sea embayment of West Antarctica is in a prominent location for a series of tectonic and magmatic events from Paleozoic to Cenozoic times. Seismic, magnetic and gravity data from the embayment and Pine Island Bay (PIB) reveal the crustal thickness and some tectonic features. The Moho is 24-22 km deep on the shelf. NE-SW trending magnetic and gravity anomalies and the thin crust indicate a former rift zone that was active during or in the run-up to breakup between Chatham Rise and West Antarctica before or at 90 Ma. NW-SE trending gravity and magnetic anomalies, following a prolongation of Peacock Sound, indicate the extensional southern boundary to the Bellingshausen Plate which was active between 79 and 61 Ma.

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

“…Dalziel and Elliot, 1982;Grunow et al, 1991;Storey, 1991). Plate tectonic reconstructions suggest that this region was a key area for the initiation of continental breakup, that it was the location of a possible plate boundary, and that it may have been, or still is, an active branch of the West Antarctic Rift System (Dalziel, 2006;Eagles et al, 2004a;Gohl et al, 2007;Jordan et al, 2010;Larter et al, 2002;Wobbe et al, 2012). In spite of all this, little is known about the tectonic evolution and architecture of the embayment from direct study there.…”

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“…Lower crustal velocities suggest a continental affinity, which implies highly stretched continental crust or continental fragments, possibly even into the area of the seamount province. SDRs are not observed in the few existing seismic reflection profiles crossing the shelf and margin (Gohl et al, 1997a(Gohl et al, ,b, 2007bNitsche et al, 2000;Cunningham et al, 2002;Uenzelmann-Neben et al, 2007).…”

“…The same approach was applied for the closest fit between Chatham Rise and eastern MBL. However, new deep crustal seismic data from the Amundsen Sea indicate that the inner to middle shelf of the Amundsen Sea Embayment consists of crust thinned to about 21-to 23-km thickness with a pre-or syn-breakup failed rift structure (Gohl et al, 2007b). Here the continental margin structure is rather complex due to the propagating and rotating rifting processes between the breakup of Chatham Rise from the western Thurston Island block at about 90 Ma (Eagles et al, 2004), the opening of the Bounty Trough between Chatham Rise and Campbell Plateau (Eagles et al, 2004;Grobys et al, 2007), and the initiation of the breakup of Campbell Plateau from MBL at about 84-83 Ma (e.g., Larter et al, 2002;Eagles et al, 2004).…”

“…Here the continental margin structure is rather complex due to the propagating and rotating rifting processes between the breakup of Chatham Rise from the western Thurston Island block at about 90 Ma (Eagles et al, 2004), the opening of the Bounty Trough between Chatham Rise and Campbell Plateau (Eagles et al, 2004;Grobys et al, 2007), and the initiation of the breakup of Campbell Plateau from MBL at about 84-83 Ma (e.g., Larter et al, 2002;Eagles et al, 2004). The analysis of a crustal seismic refraction profile (Gohl et al, 2007b) and a seismic reflection dataset (Gohl et al, 1997b) between the shelf edge and the Marie Byrd Seamount province reveals that the crust in this corridor is 12-18 km thick, highly fractured, and volcanically overprinted. Lower crustal velocities suggest a continental affinity, which implies highly stretched continental crust or continental fragments, possibly even into the area of the seamount province.…”

Chapter 5 Cenozoic Climate History from Seismic Reflection and Drilling Studies on the Antarctic Continental Margin

“…These regions include similar geomorphic and stratigraphic features. Although we do not include them in the discussion below due to space considerations, we include here representative citations to some of the studies published for the Bellingshausen and Amundsen seas Tucholke and Houtz, 1976;Tucholke, 1977;Kimura, 1982;Yamaguchi et al, 1988;Cunningham et al, 1994Cunningham et al, , 2002Gohl et al, 1997Gohl et al, , 2007Nitsche et al, 1997Nitsche et al, , 2000Wellner et al, 2001Wellner et al, , 2006Lowe and Anderson, 2002;Ó Cofaigh et al, 2005;Dowdeswell et al, 2006;Evans et al, 2006;Scheuer et al, 2006a, b;Larter et al, 2007;Uenzelmann-Neben et al, 2007) and for offshore areas of Queen Maud Land and Enderby Land (Kuvaas et al, 2004a(Kuvaas et al, , b, 2005Hinz et al, 2005;Stagg et al, 2004a, b;Leitchenkov et al, 2007;Solli et al, 2007a, b, c).…”