GONDWANALAND FRAGMENTATION AND THE ROLE OF WEST ANTARCTICA: A TECTONIC AND PALEOMAGNETIC VIEWPOINT

The efforts by Ian Dalziel, his students and colleagues helped propel a major advance in our understanding of West Antarctica’s role during Gondwanaland breakup. Dalziel recognized the critical relationship between the West Antarctica terranes and the opening history of the southern oceans during breakup.

West Antarctica consists of four topographically distinct blocks or terranes: the Antarctic Peninsula (AP) which is composed of primarily Mesozoic and Cenozoic magmatic arc, accretionary prism and back-arc basin rocks; Thurston Island/Jones Mountains (TI) consisting primarily of Mesozoic and Cenozoic magmatic arc rocks; Marie Byrd Land (MBL) consisting primarily of Mesozoic magmatic arc but also Paleozoic rocks with similarities to rocks in New Zealand and North Victoria Land; and the Ellsworth-Whitmore Mountains (EWM) with 1 billion old basement and a Paleozoic sedimentary succession similar to that found in the Pensacola Mountains in East Antarctica.

Ian led multinational research teams of structural geologists, stratigraphers, geochronologists, petrologists and paleomagnetists with an objective to create an integrated tectonic understanding of the evolution of West Antarctica. Prior to Ian’s work, most Gondwanaland reconstructions showed a space problem when reconstructing Antarctica to South America because either the AP overlapped the Falkland Plateau or was located on the western side of Chile creating a double arc. One way to create space was to rotate the EWM block by 90 degrees to a position along East Antarctica that aligned not only Gondwanide structural trends but also stratigraphic sequences. Understanding how the West Antarctic terranes moved relative to each other and to East Antarctica and South America has implications for the oceanographic linkage between the Pacific and Atlantic oceans. The existence of a sea connection would strongly influence the sedimentologic, climatic and paleontologic history of this part of Gondwanaland. Ian’s contributions have been the building blocks to new research in the region. A review will be made of models related to the movement of the West Antarctic blocks.