Abstract

For the Permian to Jurassic time interval Tethyan marine invertebrate faunas, which are generally accepted as having lived at low latitude, can be distinguished from less diverse higher latitude faunas. Displacement of these low-latitude faunas to positions of high latitude around the Pacific margins therefore provides key evidence for the movement of so-called suspect or displaced terranes. The fullest story so far has been worked out for the western margin of N America, as far north as southern Alaska, but there is also convincing evidence for the substantial northward movement of continental segments along the NE Asian margin. As regards the Southern Hemisphere the Torlesse Terrane of New Zealand appears to have moved a considerable distance southwards, but there is no fauna1 evidence of comparable far-travelled suspect terranes along the Andean margin of South America. Not only Tethyan and Boreal but E and W Pacific elements are detectable in the faunas, and the distribution of these argues for a Panthalassia studded with islands of various sizes fringing the adjacent continents, rather than for the disintegration of a single continent—Pacifica.