PRECAMBRIAN SCOTLAND AS A LAURENTIA-GONDWANA LINK - ORIGIN AND SIGNIFICANCE OF CRATONIC PROMONTORIES

Refinement of the supercontinental reconstruction for the latest Preca mbrian that places the Labrador-Greenland promontory of Laurentia with in the Arica embayment along the margin of the Gondwana craton juxtapo ses the Rockall microcontinent and northwestern British Isles with the continental margin of Peru. The conjugate cratonic margin to the nort hwest Caledonian foreland, the Hebridean shield, may have been Amazoni a. Possible South American correlatives of the Precambrian Moinian and Dalradian complexes of the Scottish Highlands can be identified in th e reconstruction; notably, there are possible equivalents of the ''old er granites'' within the Moinian and of Dalradian glacial deposits. Th erefore, the well-studied Precambrian rocks of the Scottish Highlands provide critical tests for the suggested reconstruction. The latest Pr ecambrian setting of the Arequipa massif with respect to the Gondwana craton margin and the Paleozoic intracratonic basin of Peru-Bolivia be ars a striking similarity to the early Mesozoic setting of the Rockall Plateau and northwestern British Isles with respect to the European c ontinental margin and the North Sea-Western Approaches graben system. In each case rifting appears to have been controlled by the youngest, and presumably weakest, lithosphere, but the extremity of the Labrador -Scotland-Greenland promontory was detached during final continental s eparation in Vendian to earliest Cambrian time to form the Arequipa ma ssif and in Jurassic time to form the Hebridean shield. The promontory may have played an important tectonic role through at least 1 b.y. of Earth history including influence on the development of the Andean Co rdillera. Features of this type likely have played a major role in the development of orogenic belts of all ages.