Reconstructions

Interpretations of the tectonothermal evolution of the peri-Gondwanan terranes imply a genetic relationship with the northern margin of Gondwana (present coordinates) for the entire Neoproterozoic. For example, most models for the main phase (ca. 640-570 Ma) of arc-related peri-Gondwanan magmatism require that these terranes were distributed along the northern Gondwanan margin (present coordinates), and were therefore moving with Gondwana during this time period. Hence, models for the tectonothermal evolution of the peri-Gondwanan terranes should be testable against the paleomagnetically constrained movements of the Amazonian and West Africa cratons.

Unfortunately, reliable data from these cratons is sparse, so that these connections cannot be tested directly. Most global-scale reconstructions imply a connection between Amazonia, Laurentia and Baltica throughout the Neoproterozoic, for which some paleomagnetic constraints exist. However, there is considerable disagreement concerning the paleolatitude of Laurentia during a critical time interval between 625 and 550 Ma. There are two reliable paleomagnetic poles from Laurentia for this time interval Ð one is from the 577 Ma Callander Complex (Symons and Chaisson, 1991), another from the Sept Iles intrusion (Tanczyk et al, 1987), dated at 565 Ma (Higgins and van Breeman, (1998). As it is impossible to incorporate them into the same tectonic model, two models (with high- and low-latitude position of Laurentia, respectively) were used (Pisarevsky et al., 2000, 2001).

The following reconstructions are an initial attempt to evaluate such connections and to identify critical areas of uncertainty that require resolution. We apply two approaches to each model. In the first, we assign the minimum movement to Laurentia and Gondwana required to satisfy the paleomagnetic data and then examine the relationship between this motion and the contemporary tectonothermal evolution of the peri-Gondwanan terranes. In the second, we again satisfy the paleomagnetic data but in those time periods for which there is no data we allow Laurentia and Gondwana to migrate in a fashion compatible with the tectonothermal history of the peri-Gondwanan terranes. For each approach, we provide alternative reconstructions for the high latitude and low latitude positions of Laurentia in the 625-550 Ma time interval, making a total of four animations. (Figures 2, 3, 4, and 5)