Ambiguous palaeogeographic interpretations
The major problem remains of how to account for the previously claimed alignment of Sibu- masu with North China/Australia rather than South China (Laurie and Burrett, 1992) It is compounded by the intercalation, on present geography, of the Indo-China terrane between Sibumasu and South China. This terrane has not been discussed previously in this review The Ordovician succession in the Indo-China terrane is dominated by clastic rocks, and lacks thick, platform carbonates of Thung Song type A re- cent review (Zhou et al, 1997) shows that the trilobite faunas are dominated by genera (even species) known from cool water palaeolatitudes of western Gondwana. Thus it seems probable that the Indo-China terrane had an Ordovician position well distant and to the west of where it is now, only interpolating itself in its present position between Sibumasu and China by sub- sequent transcurrent movement along the mar- gin of Gondwana.The close juxtaposition today of trilobite species similar to those found near the Ordovician pole in Indo-China with litholo- gies and faunas of undoubted Ordovician tropi-