Summary of palaeomagnetic results from West Antarctica: implications for the tectonic evolution of the Pacific margin of Gondwana during the Mesozoic

Abstract

Marie Byrd Land (MBL) is the western keystone of West Antarctica. Recent palaeomagnetic results from Lower Cretaceous (c. 117 Ma) plutonic and volcanic rocks from MBL in conjunction with a previous palaeomagnetic result from New Zealand suggest that eastern MBL and the Eastern Province of New Zealand originated in a position adjacent to Weddellia (Antarctic Peninsula, Thurston Island, and EIIsworth-Whitmore Mountains blocks) as part of a continuous Pacific convergent margin. This is far from their previously assumed position adjacent to the Western Province of New Zealand and North Victoria Land. The ll7Ma palaeomagnetic pole for eastern MBL constrains the last movements of the Weddellia blocks related to spreading in the Weddell Sea to postdate the initial opening phase of the Weddell Sea. A c. 100 Ma pole for the amalgamated mid-Cretaceous MBL is consistent with like age poles from the Thurston Island and Antarctic Peninsula blocks but all are significantly offset from a newly constructed apparent polar wander path for East Antarctica. From this it is concluded that there has been palaeomagnetically resolvable post-100Ma motion between East Antarctica and the Pacific-bordering blocks of West Antarctica as a result of extension in the Ross Sea, Ross embayment, and Byrd Subglacial Basin.