PENROSE MEDAL: OVER THE HORIZON: CONNECTING CONTINENTS IN THE GIANT FOOTSTEPS OF DU TOIT AND HOLMES
Looking again over the horizon I focused on other islands of the Scotia Ridge, and widely scattered nunataks of West Antarctica. These studies with international colleagues improved understanding of the evolution of the Scotia Arc, of implications for the onset/development of the Antarctic Circumpolar Current, and of West Antarctica as a 'collage' of displaced continental blocks that included Zealandia, significant for the history and future of the least stable part of the ice sheet.
In 1989 I Ied a field trip to the Scotia Arc. Among the participants was Eldridge Moores, and shipboard discussions indirectly evolved into his SWEAT hypothesis: that the SW United States and East Antarctica were formerly juxtaposed. The idea, elaborated upon by Paul Hoffman and myself, led to thousands of papers on pre-Pangea paleogeogrphy, supercontinents and the supercontinental cycle. My own contributions have been based largely on looking over the horizon – now from the southern United States to the Argentine Precordillera and Coats Land in Antarctica. Those 'tectonic tracers' suggest a 'southern' location for Laurentia until the opening of Iapetus, a Pacific-Iapetus seaway as the cause of the Cambrian transgression, a narrow Iapetus, and a potential Laurentia-Gondwana collision in the Ordovician.