The palaeogeography of Australasia is becom- ing progressively better understood for the 150 Ma period following the breakup of Pangaea; but there remain many unsolved problems in the Palaeozoic.The period with which we are concerned, the Ordovician (495-443 Ma), was a time of general continental dispersal (Scotese and McKerrow, 1990) long predating the assem- bly of Pangaea, and the disposition of the con- tinental masses at this time is still under investi- gation. SE Asia has been divided into a number of terranes (e.g., Mitchell, 1981; Burrett et al., 1990; Metcalfe, 1992), each bounded by major faults.These terranes have histories which are variably decoupled from that of their neigh- bours . that is, their contiguity today is no guarantee of proximity in the past.