ALBERT

Description: Benjamin Peach, John Horne and their co-workers recognized a century ago that the identical fauna and lithofacies of the lower Palaeozoic strata in the NW Highlands of Scotland and the North American craton could only be explained if they were: part of one and the same geological and zoological province'. In this sense their work provided critical geological underpinning for the subsequent understanding of Mesozoic-Cenozoic seafloor spreading and continental drift. Tectonic tracers' such as the fragment of Laurentian craton in the NW Highlands of Scotland, provide the strongest evidence available for deciphering pre-Pangaea palaeogeography. The Laurentian craton appears to have left several such tectonic calling cards' in today's southern continents. Intriguingly, it is the presence in the Andean Precordillera of northwestern Argentina of an early Palaeozoic fauna identical to that of the NW Highlands that provides perhaps the most unequivocal geological clue to pre-Pangaea palaeogeography. Recent work in East Antarctic and Laurentian cratons has provided a positive test of the hypothesis that they were once juxtaposed prior to the Neoproterozoic opening of the Pacific Ocean basin. Geochronology and isotope geochemistry, supported by palaeomagnetic studies indicate that the Coats Land crustal block of East Antarctica at the head of the Weddell Sea is also a fragment of the Laurentian craton. These three tectonic tracers' permit tracking of the Laurentian craton in relation to the present southern continents from the Neoproterozoic break-up of the Rodinian supercontinent to the late Palaeozoic assembly of Pangaea.