Evidence for Changing Plate Motions in the Tertiary Shimanto Belt, Japan

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9418344 Byrne Ancient deformed accretionary prisms commonly preserve patterns of multiple microstructure such as cleavage generations, fiberous overgrowths and oriented vein sets. Inversions of these kinematic indications to relative plate motions during the deformation event, which is of fundamental importance, is quite speculative due to lack of rigorous tests of the hypothesis that they accurately reflect such motions. This project will examine the pattern of overprinting fabrics and kinematic indicators from the Shimanto Belt of Southwest Japan, an example selected because of a well-known and significant change in convergence directions during the deformation of the Belt, and because this well exposed area has recieved considerable geologic study. Results should provide a clear test of the idea that such features can be inverted to obtain the relative convergence directions between the plates involved. Success in assessing the degree to which such inversion results in accurate plate motions will be widely applicable to other origins.