Figure 1. Iapetus Ocean and environs during Tremadoc (earliest Ordovician) times. Modified from Cocks & Fortey (1982)'s Arenig palaeogeographic reconstruction by reversing their rate of closure (2 cm/yr) for the duration of the Tremadoc. The palaeogeographic positions for the Tremadoc are essentially the same as reported by Scotese (1986, p. 759). They differ from Parrish (1982) who for the Franconian (Late Cambrian) placed Balto-Scandia west of Laurentia using Scortese et al. (1979) earlier views. Non-Signature Locales: B. Belgium; 1, Levis, Quebec; M, Matane, Quebec; NY, New York; W. Wales. Signature Locales: D, Denmark; E, Estonia; NB1, Saint John, New Brunswick, positioned by geochemical affinities; NB2 Saint John, New Brunswick positioned attached to Maguma; O. Oslo; S. Sweden. Oceanic currents and Ekman transport derived by assumption of Sverdrup-style geostrophic circulation about oceanic high pressure centred at 30° S and low pressure centred at 0° and 60° S.