Abstract:
A recent re-evaluation of the Late Mesozoic and Cenozoic sea-floor spreading data in the eastern Pacific has allowed us to make a new interpretation of the timing and sequence of the tectonic events which produced the present configuration of the plates. Rotation parameters specifying the relative motion between all pairs of plates in the ocean basin have been calculated from the best fit of oceanic magnetic anomalies, with additional input from bathymetry and crustal ages of the Deep Sea Drilling Project sites. The rotation parameters for the relative motion between the Pacific and Antarctic plates, and the continental rotation parameters, are taken from previous publications. Plate motions have been determined back to 74 Ma. This time marks the initiation of spreading at the Pacific-Antarctic Ridge which caused the separation of the Campbell Plateau from Antarctica. Thus, this time is the earliest fix on the position of the Pacific plate relative to the continents surrounding the Pacific Ocean basin using sea-floor spreading. Since it is not possible to derive quantitative information about the relative motion between two plates separated by a trench, all rotations for the oceanic plates of the Pacific basin have been calculated relative to the Pacific plate and then relative to North America through the plate circuit. Since we also know the relative position of North America with respect to the other continents, we can show the relative position of the Pacific plate and the other oceanic plates with respect to all of the continental plates surrounding the Pacific Ocean basin.