EVIDENCE OF TRANSPRESSION ALONG THE CLIPPERTON TRANSFORM - IMPLICATIONS FOR PROCESSES OF PLATE BOUNDARY REORGANIZATION

High-resolution bathymetry data of the Clipperton Fracture Zone and fo cal mechanisms of recent earthquakes along the active transform provid e evidence for recent and ongoing transpression along the Clipperton T ransform. Structural and morphological features observed in the bathym etry data include: normal and strike-slip faults oriented obliquely to the strike of the transform; curved trends of abyssal hills produced by simple shear of the lithosphere bordering the transform fault; abys sal hills offset by obliquely trending strike-slip faults on lithosphe re bordering the transform; and lithospheric flexure and associated vo lcanism near the active transform. All of these features can be explai ned by a transpression scenario in which a counter-clockwise change in spreading direction of similar to 5 degrees began about 0.4-0.5 Ma an d subjected the right-stepping Clipperton Transform to compression. A comparison of the median ridge volume to calculated estimates of the c onvergent volume predicted by the transpression scenario indicates tha t the median ridge is likely to be a product of the brittle deformatio n associated with transpression. The convergent volume estimates sugge st that larger spreading direction changes (similar to 5 degrees) do n ot occur instantaneously. Instead, spreading direction changes begin s lowly and accelerate to the new spreading direction once compression a cross the transform has ceased. Many of the structures observed along the Clipperton Transform are very similar to features observed along o ther known convergent transforms, such as the San Andreas Fault in Cal ifornia, and may have important implications for understanding contine ntal transforms. The transpression scenario also indicates that transf orms are very important in constraining the rate and character of glob al plate motion changes.