Logo Earthworks
Show/Hide Menu
Home
Gondwana
News
Publications
About
Contact

Retracing Ocean Fracture Zones

Telescoping Transforms
Where mid-ocean ridges are offset by transforms, the extinct (aseismic) sections of the transform are left behind, growing steadily in length as each of the pair of conjugate continents retreats from the mid-ocean ridge. If we wish to reconstruct the paleo-positions of the continents we have to honour this process and retrace extinct fracture zones by telescoping them into each other, reversing the process of their creation. To do this in practice on a map, lengths of the fracture zone have to be time-windowed so that they disaapear progressively when maps are drawn of earlier times when the younger sections did not yet exist. And, of course, each section of fracture zone has to be attached to the appropriate continental fragment. The reconstruction model then has to be built so that the fracture zones remain coincident and colinear. This proves to be a major constraint on paelopositions, arguably more important than the coincidence of marine magnetic anomalies, and the only positional constraint available during the Cretaceous Quiet Zone (121.4 to 83.64 Ma). This process is helped by using Euler interval poles since the Euler latitude lines (or small circles) about these poles are always parallel to the lengths of fracture zones in the time interval to which they apply. The available magnetic anomalies must, of course, be used to calibrate this process against time. The animation shows the result of adjusting the rotation parameters of all the fragments of Gondwana as carefully as possible to ensure that the model passes this test of validity.
Refer Reeves & de Wit, 2000.
::